T 135 2  6 
B7A5 


"^^   BOSTON  I A    4^^ 

SJ^j^*  C0ND)TA  A  D  ^/AiW 


llol^^o!!^"'' 


Plate  XVI 


MAIN    DRAINAGE    WORKS 


OF     THE 


CITY    OF    BOSTON 

{MASSAGEUSETTS,     U.S.A.) 


BY 

ELIOT     C.    CLAEKE     ?^ 

Principal    Assistant    Engineer,    in    charge 


BOSTON 
ROCKWELL    AND    CHUECHILL,    CITY    PRINTERS 

No.     39    Abch    Street 

1885 


BOSTON  COLLEGE  I|gBAf,J 
CHEiSTiiUT  HILL,  MA«9, 


Digitized  by  tine  Internet  Archive 

in  2010  with  funding  from 

Boston  Library  Consortium  IVIember  Libraries 


A 

http://www.archive.org/details/maindrainageworkclar 


PREFACE. 


This  brief  description  of  the  Main  Drainage  Works,  of  Bos- 
ton, aims  to  record,  for  the  benefit  of  engineers,  an  account  of 
the  engineering  problems  involved  and  the  methods  of  construc- 
tion adopted.  It  also  aims  to  give  to  the  tax-payers  and  gen- 
eral public  a  descriptive  account  of  why  the  large  appropriation 
for  "An  Improved  System  of  Sewerage  "  was  needed,  and  how 
it  has  been  spent.  By  attempting  to  accomplish  both  of  these 
purposes  it  fulfils  neither  of  them  adequately ;  since  one  class 
of  readers  will  find  it  too  technical,  and  the  other  too  deficient 
in  detail.  It  has  been  prepared  amid  pressing  engagements, 
and  to  save  time  the  writer  has  not  hesitated  to  borrow  freely 
from  previous  reports,  by  himself  and  others.  Traces  of  such 
compilation  will,  doubtless,  be  noticed  by  the  discerning.  It  is 
hoped  that  a  fair  idea  of  the  works  can  be  obtained  from  the 
illustrations  ;  and  that  the  description,  even  by  its  defects,  may 
encourage  other  engineers  to  publish,  as  they  too  seldom  do, 
accounts  of  works  with  which  they  have  been  connected. 

E.  C.  C. 

Boston,  April,  1885. 


TABLE  OF  CONTENTS. 


PAGE 

CHAPTER    I. 

Early   history    of   sewerage   at   Boston     ......  7 


CHAPTER    11. 
Character   and  defects   of   the   old   sewerage   system   ...         12 

CHAPTER    III. 
Movements   for  reform  —  Commission   of   1875 16 

CHAPTER    IV. 
Preliminary   investigations 22 

CHAPTER    V. 
Main   sewek 31 

CHAPTER    VI. 
Intercepting   sewers 37 

CHAPTER    VII. 

PUMPING-STATION 53 

CHAPTER    VIII. 
Outfall   sewer 62 

CHAPTER    IX. 
Reservoir  and   outlet    ..........         76 

CHAPTER    X. 
Details    of  engoeerino   and   construction        .....        83 


6  CONTENTS. 

PAGE 

CHAPTER    XI. 
Working   of   the   new   system .        93 


APPENDIX    A. 


Record    op    tests    of    cement    made    for  Boston  Main  Drainage 

Works 113 

APPENDIX    B. 

List   of  officers   connected  with  Boston  Main  Drainage  Works,       140 


MAIN  DRAINAGE   WORKS. 


CHAPTEE  I. 

EAELY    HISTOEY    OF    SEWERAGE    AT    BOSTON. 

The  conditions  which  necessitated  a  change  in  the  system  of 
sewage  disposal  at  Boston,  and  the  problems  to  be  solved  in 
making  that  change,  can  be  better  understood  after  a  brief  con- 
sideration of  the  early  history  of  sewerage  at  that  city  and  the 
manner  in  which  the  sewers  were  originally  built. 

Boston  was  first  settled  in  1630.  When  the  first  sewer  was 
built  cannot  now  be  determined,  but  it  was  earlier  than  the 
year  1700,  for  already,  in  1701,  the  population  being  about 
8,000,  a  nuisance  had  been  created  by  frequent  digging  up  of 
streets  to  lay  new  sewers  and  to  repair  those  previously  built ; 
and  in  town  meeting,  September  22,  1701,  it  was  ordered, 
"  That  no  person  shall  henceforth  dig  up  the  Ground  in  any  of 
the  Streets,  Lanes  or  High-way es  in  this  Town,  for  the  laying  or 
repairing  any  Drain,  without  the  leave  or  approbation  of  two 
or  more  of  the  Selectmen." 

The  way  in  which  sewers  were  built  at  this  time  was,  appar- 
ently, this.  When  some  energetic  householder  on  any  street 
decided  that  a  sewer  was  needed  there,  he  persuaded  such  of 
his  neighbors  as  he  could  to  join  him  in  building  a  street  drain. 
Having  obtained  permission  to  open  the  street  or  perhaps 
neglected  this  preliminary,  they  built  such  a  structure  as  they 
thought  necessary,  on  the  shortest  line  to  tide-water.  The  ex- 
pense was  divided  between  them,  and  they  owned  the  drain 
absolutely.  Should  any  new-comer,  or  any  neighbor,  who  had 
at  first  declined  to  assist  in  the  undertaking,  subsequently  desire 
to  make  use  of  the  drain,  he  was  made  to  pay  for  the  privilege 


b  MAIN   DEAINAGE   WORKS. 

what  the  proprietors  saw  fit  to  charge.  When  a  drain  needed 
repairing  all  persons  using  it  were  expected  to  pay  their  share 
of  the  cost. 

As  might  have  been  expected,  under  such  a  system,  great 
difficulty  was  experienced  in  distributing  fairly  the  expenses 
and  in  collecting  the  sums  due  ;  so  that  it  became  of  sufficient 
importance  to  engage  the  attention  of  the  Legislature,  and  in 
1709  an  act  was  passed  regulating  these  matters.  It  is  entitled, 
"  An  Act  —  Passed  by  the  Great  and  General  Court  or  Assem- 
bly of  Her  Majesty's^  Province  of  the  Massachusetts-Bay.  For 
regulating  of  Drains  and  Common  Shores.^  For  preventing  of 
Inconveniences  and  Dammages  by  frequent  breaking  up  of 
High-Wayes  ....  and  of  Difi'erences  arising  among 
Partners  in  such  Drains  or  common  Shores  about  their  Propor- 
tion of  the  Charge  for  making  and  repairing  the  same." 

The  act  recites  that  no  person  may  presume  to  break  up  the 
ground  in  any  highway  within  any  town  for  laying,  repairing 
or  amending  any  common  shore,  without  the  approbation  of  the 
selectmen,  on  pain  of  forfeiting  20  shillings  to  the  use  of  the 
poor  of  said  town  ;  that  all  such  structures,  for  the  draining  of 
cellars,  shall  be  "  substantially  done  with  brick  or  stock ;"  ^ 
that  it  shall  be  lawful  for  any  inhabitant  of  any  town  to  lay  a 
common  shore  or  main  drain,  for  the  benefit  of  themselves  and 
others  who  shall  think  fit  to  join  therein,  and  every  person  who 
shall  afterwards  enter  his  or  her  particular  drain  into  such  main 
drain,  or  by  any  more  remote  means  receives  benefit  thereby, 
for  the  drainage  of  their  cellars  or  lands,  shall  be  obliged  to 
pay  unto  the  owner  or  owners  a  proportionate  part  of  the  charge 
of  making  or  repairing  the  same,  or  of  that  part  of  it  below 
where  their  particular  drain  enters.  In  case  of  dispute  the 
selectmen  decided  how  much  each  person  should  pay,  and  there 
was  an  appeal  from  their  decision  to  the  courts. 

For  one  hundred  and  fifteen  years  the  sewers  in  Boston  were 
built,  repaired,  and  owned  by  private  individuals  under  author- 
ity of  this  act. 

It  may  be  doubted  if  most  of  them  were  "substantially  done 
with  brick  or  stock,"  and  there  certainly  was  much  difficulty 

^Anne.  ^Sewers.  ^  Stone. 


Plate   I. 


MAP    OF 
1775. 


SCALE 


Yzmtt 


EARLY   HISTORY    OF    SEWERAGE    AT    BOSTON.  9 

about  payments ;  so  that  in  1763  the  act  of  1709  was  amended, 
the  amendment  reciting  that  "  Whereas  it  frequently  happens 
that  the  main  drains  and  common  shores  decay  or  fill  up     . 

.  and  no  particular  provision  is  made  by  said  act  to  com- 
pel! such  persons  as  dwell  below  that  part  where  said  common 
shores  are  repaired,  and  have  not  sustained  damage,  to  pay 
their  proportionable  share  thereof,  as  shall  be  adjudged  by  the 
selectmen,  which  has  already  occasioned  many  disputes  and 
controversies,"  therefore  it  was  decreed  that  in  future  all  per- 
sons benefited  should  pay  for  repairs. 

No  further  change  was  made  till  1796,  and  then  only  to 
provide  that  persons  who  did  not  pay  within  ten  days  of  notifi- 
cation should  pay  double,  and  that  the  sewers,  besides  being  of 
brick  or  stone,  might  be  built  of  such  other  material  (probably 
wood)  as  should  be  approved  by  the  selectmen. 

Under  this  act  the  greater  part  of  Boston  was  sewered  by 
private  enterprise.  The  object  for  which  the  sewers  were  built 
was,  as  indicated  "for  the  draining  of  cellars  and  lands."  The 
contents  of  privy-vaults,  of  which  every  house  had  one,  and 
even  the  leakage  from  them,  were  excluded ;  but  they  received 
the  waste  from  pumps,  and  kitchen  sinks,  and  also  rain-water 
from  roofs  and  yards. 

That  much  refuse  got  into  them  is  proved  b}^  their  frequently 
being  filled  up,  and  as  they  had  a  very  insufficient  supply  of 
water  they  were  evidently  sewers  of  deposit.  That  they 
served  their  purpose  at  all  is  due  to  the  fact  that  the  old  town 
drained  by  them,  as  shown  in  Plate  I.,  consisted  of  hills  with 
good  slopes  on  all  sides  to  the  water.  Of  this  early  method  of 
building  sewers  Josiah  Quincy,  then  Mayor,  said,  in  1824  : 
"No  system  could  be  more  inconvenient  to  the  public,  or  embar- 
rassing to  private  persons.  The  streets  were  opened  with  little 
care,  the  drains  built  according  to  the  opinion  of  private  in- 
terest or  economy,  and  constant  and  interminable  vexatious 
occasions  of  dispute  occurred  between  the  owners  of  the  drain 
and  those  who  entered  it,  as  to  the  degree  of  benefit  and  pro- 
portion of  contribution." 

In  1823  Boston  obtained  a  city  charter,  and  one  of  the  first 
acts  of  the  city  government  was  to  assume  control  of  all  exist- 


10  MAIN    DEAINAGE    WORKS. 

ing  sewers  and  of  the  building  and  care  of  new  ones.  The 
new  sewers  were  built  under  the  old  legislative  acts,  and 
the  whole  expense,  as  before,  was  charged  to  the  estates  bene- 
fited, being  divided  with  reference  to  their  assessed  valuation. 
A  small,  variable  portion  of  the  cost  was,  however,  generally 
assumed  by  the  city,  in  consideration  of  its  use  of  the  sewers 
for  removing  surplus  rain-water  from  the  public  streets. 

The  city  ordinances  regulating  sewers  required  that,  when 
practicable,  they  should  be  of  sufficient  size  to  be  entered  for 
cleaning.  Some  supervision  was  exercised  over  connecting 
house-drains,  and,  if  thought  necessary,  a  strainer  could  be  placed 
on  each.  Fecal  matters  were  rigidly  excluded  until  1833,  when 
it  was  ordered  that,  while  there  must  be  no  such  connection 
between  privy-vaults  and  drains  as  would  pass  solids,  the 
Mayor  and  Aldermen,  at  their  discretion,  might  permit  such 
a  passage  or  connection  as  would  admit  fluids  to  the  drain. 
This  action  was  perhaps  due  to  an  advent  of  cholera  during  the 
previous  year.  To  assist  in  flushing  out  deposits,  it  was  pro- 
vided, in  1834,  that  any  person  might  discharge  rain-water  from 
his  roof  into  the  sewers,  without  any  charge  for  a  permit.  The 
same  year  control  of  the  sewers  and  sewer-assessments  was 
given  to  the  City  Marshal.  He  was  especially  to  devote  him- 
self to  the  collection  of  assessments,  new  and  old,  which  were 
largely  unpaid.  The  other  duties  of  the  marshal  probably  pre- 
vented him  from  devoting  sufficient  energy  to  the  accomplish- 
ment of  this  task ;  for  it  appears  that,  while  there  had  been 
expended  by  the  city,  for  building  sewers,  from  1823  to  1837, 
the  sum  of  $121,109.52,  there  had  been  collected  of  this  sum 
but  $26,431.31. 

That  there  might  be  some  one  to  give  his  whole  time  to  the 
financial  and  administrative  duties  connected  with  the  sewer- 
age system,  a  "  Superintendent  of  Sewers  and  Drains "  was 
appointed  in  July,  1837.  He  was  empowered  to  assess  the 
whole  cost  of  any  new  sewer  upon  the  real  estate,  including 
buildings  benefited  by  it.  In  1838  the  city  decided  to  assume 
one-quarter  of  the  gross  cost;  and  in  1840,  in  obedience  to  a 
decision  by  the  Supreme  Court,  it  was  ordered  that  the  three- 
quarters  of  the  cost  of  sewers  which  was  to  be  paid  by  the 


EARLY   HISTORY    OF    SEWERAGE    AT    BOSTON.  11 

abutters,  should  be  assessed  with  reference  to  the  value  of 
the  land  only,  without  taking  into  consideration  the  value  of 
buildings  or  other  improvements,  and  such  has  been  the  prac- 
tice up  to  the  present  time. 

It  is  estimated  that  there  are  at  the  present  time  (1885) 
about  226  miles  of  sewers  in  Boston.  In  1873  there  were 
about  125  miles,  and  in  1869  about  100  miles.  There  are  at 
present  supposed  to  be  more  than  100,000  water-closets  in  use 
in  the  city ;  in  1857  there  were  6,500. 


12  MAIN   DRAINAGE   WORKS. 


CHAPTER  II. 

CHARACTER    AND    DEFECTS    OF    THE    OLD    SEWERAGE    SYSTEM. 

Such  changes  have  taken  place  in  the  contours  of  the  city, 
through  operations  for  reclaiming  and  filling  tidal  areas  border- 
ing the  old  limits,  that,  from  being  a  site  easy  to  sewer,  Boston 
became  one  presenting  many  obstacles  to  the  construction  of  an 
efficient  sewerage  system. 

This  will  be  understood  from  an  examination  of  the  plan  of 
the  city  proper,  Plate  V.  On  this  plan  the  shaded  portion  rep- 
resents the  original  area  of  the  city,  and  very  nearly  its  limits 
in  1823.  The  unshaded  portion  of  the  plan,  indicating  present 
limits,  consists  entirely  of  reclaimed  land  filled  to  level 
planes  little  above  mean  high  water,  the  streets  traversing  such 
districts  being  seldom  more  than  seven  feet  above  that  eleva- 
tion. A  large  proportion  of  the  house  basements  and  cellars 
in  these  regions  are  lower  than  high  water,  and  many  of  them 
are  but  from  five  to  seven  feet  above  low-water  mark,  the  mean 
rise  and  fall  of  the  tide  being  ten  feet.  This  lowness  of  land 
surface  and  of  house  cellars  necessitates  the  placing  of  house- 
drains  and  sewers  at  still  lower  elevations.  Most  house-drains 
are  under  the  cellar  floors,  and  fall  in-  reaching  the  street  sew- 
ers ;  the  latter  must  be  still  lower,  and  in  their  turn  fall 
towards  their  outlets,  which  were  rarely  much,  if  at  all,  above 
low  water. 

Moreover,  as  filling  progressed  on  the  borders  of  the  city,  it 
became  necessary  to  extend  the  old  sewers  whose  outlets  would 
have  been  cut  off.  The  old  outlets  being  generally  at  a  low 
elevation,  even  where  the  sewers  themselves  were  sufficiently 
hio-h,  the  extensions  had  to  be  built  still  lower,  and  when  of 
considerable  length  could  have  bilt  little  fall  towards  the  new 
mouths. 

As  a  consequence,  the  contents  of  the  sewers  were  dammed 
back  by  the  tide  during  the  greater  part  of  each  twelve  hours. 


CHARACTER  AND  DEFECTS   OF  THE   OLD  SEWERAGE   SYSTEM.    13 

To  prevent  the  salt  water  flowing  into  them  many  of  them 
were  provided  with  tide-gates,  which  closed  as  the  sea  rose,  and 
excluded  it.  These  tide-gates  also  shut  in  the  sewage,  which 
accumulated  behind  them  along  the  whole  length  of  the  sewer, 
as  in  a  cesspool ;  and,  there  being  no  current,  deposits  occurred. 
The  seAvers  were,  in  general,  inadequately  ventilated,  and 
the  rise  of  sewage  in  them  compressed  the  foul  air  which 
they  contained  and  tended  to  force  it  into  the  house  connec- 
tions. To  aiford  storage  room  for  the  accumulated  sewage, 
many  of  the  sewers  were  built  very  much  larger  than  would 
otherwise  have  been  necessary,  or  than  was  conducive  to  a 
proper  flow  of  the  sewage  ;  and,  as  there  would  have  been  little 
advantage  in  curved  inverts  where  there  was  to  be  no  cur- 
rent, flat-bottomed  and  rectangular  shapes  were  frequently 
adopted. 

Although  at  about  the  time  of  low  water  the  tide-gates 
opened  and  the  sewage  escaped,  the  latter  almost  immediately 
met  the  incoming  tide,  and  was  brought  back  by  it,  to  form 
deposits  upon  the  flats  and  shores  about  the  city.  Of  the  large 
amount  of  sewage  which  flowed  into  Stony  Brook  and  the  Back 
Bay,  and  especially  that  which  went  into  South  Bay,  between 
Boston  proper  and  South  Boston,  hardly  any  was  carried 
away  from  the  vicinity  of  a  dense  population. 

The  position  of  the  principal  sewer  outlets  and  of  the  areas 
on  which  the  sewage  which  caused  most  ofl'ence  used  to  accu- 
mulate, is  indicated  on  Plate  V.  From  these  places  foul- 
smelling  gases  and  vapors  emanated,  which  were  diftused  to  a 
greater  or  less  distance,  according  to  the  state  of  the  tempera- 
ture or  of  the  atmosphere.  Under  certain  conditions  of  the 
atmosphere,  especially  on  summer  evenings,  a  well-defined 
sewage  odor  would  extend  over  the  whole  South  and  West 
Ends  of  the  city  proper. 

This  evil  was  thus  described  by  the  City  Board  of  Health  in 
one  of  their  annual  reports  :  — 

Complaints  of  bad  odors  have  been  made  moi*e  frequently  dm'ing  the 
past  year  than  ever  before. 

They  have  come  from  nearly  all  jiarts  of  the  city,  but  es2:)ecial]y  and 
seriously  from  the  South  and  West  Ends, 


14  MAIN    DRAINAGE    WORKS. 

Large  territories  have  been  at  once,  and  frequently,  enveloped  in  an 
atmosphere  of  stench  so  strong  as  to  arouse  the  sleeping,  terrify  the  weak, 
and  nauseate  and  exasjaerate  everybody. 

It  has  been  noticed  more  in  the  evening  and  by  night  than  during  the 
day ;  although  there  is  no  time  in  the  whole  day  when  it  may  not  come. 

It  visits  the  rich  and  the  poor  alike.  It  fills  the  sick-chamber  and  the 
office.  Distance  seems  to  lend  but  little  protection.  It  travels  in  a  belt 
half-way  across  the  city,  and  at  that  distance  seems  to  have  lost  none  of  its 
potency,  and,  although  its  source  is  miles  away,  you  feel  sure  it  is  directly 
at  your  feet 

The  sewers  and  sewage  flats  in  and  about  the  city  furnish  nine-tenths  of 
all  the  stenches  complained  of. 

They  are  much  worse  each  succeeding  year ;  they  will  be  much  worse 
next  3^ear  than  this. 

The  accumulation  of  sewage  upon  the  flats  and  about  the  city  has  been, 
and  is,  rapidly  increasing,  until  there  is  not  probably  a  foot  of  mud  in  the 
river,  in  the  basins,  in  the  docks,  or  elsewhere  in  close  proximity  to  the  city, 
that  is  not  fouled  with  sewage. 


Various  palliative  measures  were  adopted.  The  Back  Bay, 
into  which  the  waters  of  Stony  Brook,  and  with  them  most  of 
the  sewage  of  Roxbury  and  Jamaica  Plain,  used  to  empty,  was 
lately  partly  tilled  with  gravel,  forming  the  present  Back-Bay 
Park.  The  brook  was  carried  in  a  covered  channel  to  Charles 
River,  which  somewhat  lessened  the  nuisance  caused  by  it,  or  at 
least  transferred  it  to  another  locality.  Owing  to  complaints 
from  the  physicians  of  the  City  Hospital  and  other  residents  in 
that  neighborhood  the  city  purchased  and  filled  the  upper  por- 
tion of  Old  Roxbury  Canal  at  the  head  of  South  Bay.  The 
sewers  emptying  into  it  were  extended,  and  the  position  of  the 
nuisance  caused  by  them  was  thus  altered  by  a  few  hundred 
feet.  In  general  terms  it  may  be  said  that  none  of  the  old 
sewer  outlets  were  in  unobjectionable  locations. 

There  are  no  plans  in  detail  of  the  sewers  of  Boston.  Many 
of  the  older  ones  have  no  man-holes.  In  some  streets  several 
sewers  exist  side  by  side.  Occasionally  a  sewer  is  found  built 
directly  above  an  older  one.  Probably  one-half  of  the  larger 
main  sewers  are  wholly  or  partly  built  of  wood  and  have  flat 
bottoms.  An  unwise  provision  was  inserted  in  the  charters  of 
some  of  the  private  corporations  organized  for  the  purpose  of 
reclaiming  and  filling  areas  of  flats,  by  which  it  was  stipulated 


Plate  11. 


Fig,  I  Fig.  2 


Fig.  3  Fig. 4 


Fig.  9 


Fig.  15 


Fig.  17 


Fig.  10 


BOSTC 


I      O      I       2 


HOL 


ng.23       24-  25 


Fi^.l8 


F,6,.2I 


Fig.  I  Fig. 2  Fig. 3  Fig. 4  Fig.  5  Fi^.6 


Fi6.7 


Fi^.8 


Fig.  II  Fig.  12 

COMMON      TYPES 

OF 

BOSTON  CITY  SEWERS. 

SCALE, 


FigJ3 


HOUSE    DRAINS. 


27 


FiS.I6 


Fig.  19 


Fig.  14- 


28  29 


ng.2l 


Fig.  16 


Fig.  20 


Fig-  22. 


CHARACTER  AND  DEFECTS  OF  THE   OLD  SEWERAGE   SYSTEM.    15 

that  the  corporations  should  themselves  extend  all  sewers  whose 
discharge  would  be  obstructed  by  the  filling.  Such  extensions 
were  made  without  system,  by  building  flat-bottomed  wooden 
scow  sewers,  which  were  laid  upon  the  soft  surface  of  the  flats 
before  the  filling  was  done.  Cross-sections  of  various  common 
forms  of  existing  city  sewers  are  shown  on  Plate  II.,  Figs. 
1  to  22.  Fig.  22  shows  Stony-Brook  culvert,  which  consti- 
tutes the  lower  mile  of  Stony  Brook,  and  is  that  part  of  it  which 
is  covered  and  used  as  a  sewer. 

One  fact  which  increased  the  danger  arising  from  the  dam- 
ming up  of  the  sewers,  and  the  consequent  compression  of  their 
gaseous  contents,  was  that  the  house-drains  connecting  with 
these  sewers  were  ill  adapted  to  resisting  this  pressure. 
Most  of  them  were  built  of  brick  or  of  wood,  before  the  rise  of 
modern  ideas  in  regard  to  sanitary  drainage  ;  and,  as  they  were 
usually  leaky,  the  gases  forced  into  them  found  ready  egress 
into  the  houses.  Figs.  23  to  29  on  Plate  II.  show  common 
forms  of  these  house-drains. 

The  drains  differ  greatly  in  size.  Of  113  which  were  ob- 
served while  building  the  intercepting  sewers  in  1878,  — 

11  were  about  4  inches  in  diameter. 


4 

5 

21 

6 

5 

7 

27 

8 

8 

9 

11 

10 

26 

12 

or  more. 


113 


Of  these  113  drains,  9  were  level  and  14  pitched  the  wrong 
way ;  45  had  flat  bottoms  and  68  curved  ones ;  38  were 
wholly  or  partly  choked  with  sludge,  and  75  were  reasonably 
clean.  At  about  the  same  time  examinations  made  with 
peppermint,  by  the  City  Board  of  Health,  of  351  house-drains 
in  various  sections  of  the  city,  showed  that  193  of  them,  or  55 
per  cent.,  were  defective  in  regard  to  tightness. 


16  MAIN   DRAINAGE   WORKS. 


CHAPTEE  III. 

MOVEMENTS   FOR   REFORM-COMMISSION   OF    1875. 

For  the  ten  years  preceding  1875  the  average  annual  death- 
rate  of  Boston  was  about  25  m  1,000.  On  April  14,  1870,  the 
Consulting  Physicians  of  the  city  addressed  to  the  authorities  a 
remonstrance  as  to  the  then  existing  sanitary  condition  of  the 
city,  in  which  they  declared  the  urgent  necessity  of  a  better 
system  of  sewerage,  stating  that  it  would  be  a  work  of  time,  of 
great  cost,  and  requiring  the  highest  engineering  skill. 

At  about  the  same  time,  and  in  each  of  their  Annual  Eeports 
thereafter,  the  State  Board  of  Health  referred  to  the  matter, 
saying  that  the  question  of  drainage  for  Boston  and  its  immediate 
surroundings  was  of  an  importance  which  there  was  no  danger 
of  overstating. 

Of  such  great  importance  was  the  matter  considered  by  the 
State  Legislature  that,  in  the  special  session  of  1872,  an  act  was 
passed  authorizing  the  appointment  of  a  commission,  to  be  paid 
by  the  City  of  Boston,  to  investigate  and  report  upon  a  compre- 
hensive plan  for  a  thorough  system  of  drainage  for  the  metro- 
politan district.  This  was  not  accepted  by  Boston,  on  the 
ground  that  the  expense  should  be  shared  by  the  neighboring 
cities  and  towns,  and  no  commission  was  appointed. 

In  a  communication  to  the  City  Council  (Dec.  28,  1874),  up- 
on the  necessity  of  improved  sewerage,  the  City  Board  of 
Health  pointed  out  clearly  the  evils  of  the  existing  system,  and 
strongly  urged  that  a  radical  change  should  be  made.  March 
1,  1875,  an  order  passed  the  City  Council  authorizing  the  Mayor 
to  appoint  a  commission,  "  consisting  of  two  civil  engineers  of 
experience  and  one  competent  person  skilled  in  the  subject  of 
sanitary  science,  to  report  upon  the  present  sewerage  of  the 
city  ....  and  to  present  a  plan  for  outlets  and  main 
lines  of  sewers,  for  the  future  wants  of  the  city."  The  Mayor 
thereupon  appointed  as  members  of  the  commission  Messrs.  E. 


MOVEMENTS    FOR   EEFOEM-COMjMISSION    OF    1875.  17 

S.  Chesbrough,  C.E.,  Moses  Lane,  C.E.,  and  Charles  F.  Fol- 
som,  M.D.,  and  in  December  of  the  same  year  their  report  was 
submitted. 

As  was  to  be  expected  from  the  professional  attainments  and 
reputation  of  these  gentlemen,  the  report  contained  a  compre- 
hensive and  exhaustive  statement  of  the  defects  in  the  existino- 
s^^stem  of  sewerage,  and  of  the  causes  which  had  produced  such 
a  condition  of  affairs,  and  finally  recommended  for  adoption  a 
well-considered  plan  for  remedying  present  defects  and  for  pro- 
viding for  future  needs. 

The  commission  stated,  as  essential  conditions  of  efficient 
sewerage  :  first,  that  the  sewage  should  start  from  the  houses, 
and  flow  in  a  continuous  current  until  it  reached  its  destination, 
either  in  deep  water  or  upon  the  land;  and,  second,  that  the 
sewers  should  be  ventilated  so  that  the  atmosphere  in  them 
should  attain  the  highest  possible  degree  of  purity.  To  quote 
from  the  report ;  — 

The  point  Avliicli  must  be  attended  to,  if  we  would  get  increased  com- 
forts and  kixuries  in  our  houses,  Avithout  doing  so  at  cost  of  health  and  life, 
is  to  get  our  refuse  out  of  the  way,  far  beyond  any  possibility  of  harm 
before  it  becomes  dangerous  from  putrefaction.  In  the  heat  of  summer 
this  time  should  not  exceed  twelve  hours.  We  fail  to  do  this  now  in  three 
ways :  — 

First.  We  cannot  get  our  refuse  always  from  our  house-drains  to  our 
sewers,  because  the  latter  may  not  only  be  full  themselves  at  high  tide,  but 
they  may  even  force  the  sewage  up  our  drains  into  our  houses. 

Second.  We  do  not  empty  our  sewers  promptly,  because  the  tide  or  tide- 
gates  prevent  it.  In  such  case  the  sewage  being  stagnant,  a  precipitate 
falls  to  the  bottom,  which  the  slow  and  gradual  emptying  of  the  sewers,  as 
the  tide  falls,  does  not  produce  scour  enough  to  remove.  This  deposit  re- 
mains with  little  change  in  some  places  for  many  months. i 

Third.  With  our  refuse,  which  is  of  an  especially  foul  character,  once 
at  the  outlets  of  the  sewers,  it  is  again  delayed,  there  to  decompose  and 
contaminate  the  air. 

As  a  result  of  this  failure  to  carry  out  the  cardinal  rule  of  sewerage, 
we  are  obliged  to  neglect  the  second  rule,  which  is  nearly  as  important, 
namely,  ventilation  of  the  sewers ;  for  the  gases  are  often  so  foul  that  we 
cannot  allow  them  to  escape  without  causing  a  nuisance  ;  and  we  compro- 
mise the  matter  by  closing  all  the  vents  that  we  can,  with  the  certainty  of 
poisoning  the  air  of  our  houses. 

'  The  catch-  basins,  too,  in  the  course  of  the  sewers,  serve  only  to  ag-gravate  this  evil, 
and  should  be  filled  as  early  as  is  practicable. 


18  MAIN    DRAINAGE    WORKS. 

In  the  opinion  of  the  commission  there  are  only  two  ways  open  to  us. 
The  first,  raising  more  than  one-lialf  of  the  superficial  area  of  the  city 
proper  (excluding  suburbs)  is  entirely  out  of  the  question,  from  the  enor- 
mous outlay  of  money  which  would  be  required,  —  more  than  four  times  as 
much  as  would  be  needed  for  the  plan  which  we  propose,  and  which  con- 
sists in  intercepting  sewers  and  pumping. 

There  are  in  use  now  in  various  parts  of  the  world  three  methods  of 
dis^Dosing  of  the  sewage  of  large  cities,  where  the  water-carriage  system 
is  in  use  :  — 

First.  Precipitation  of  the  solid  parts,  with  a  view  to  utilizing  them  as 
manure,  and  to  purifying  the  streams. 

Second.     Irrigation. 

Neither  of  these  processes  has  proved  remunerative,  and  the  former  only 
clarifies  the  sewage  without  purifying  it ;  but  if  the  time  comes,  when,  by 
the  advance  in  our  knowledge  of  agricultural  chemistry,  sewage  can  be 
profitably  used  as  a  fertilizer,  or  if  it  should  now  be  deemed  best  to  util- 
ize it,  in  spite  of  a  pecuniary  loss,  it  is  thought  that  the  point  to  which  we 
propose  carrying  it  will  be  as  suitable  as  any  which  can  be  found  near 
enough  to  the  city,  and  at  the  same  time  far  enough  away  from  it. 

The  third  way  is  that  adopted  the  world  over  by  large  cities  near  deep 
water,  and  consists  in  carrying  the  sewage  out  so  far  that  its  point  of 
discharge  will  be  remote  from  dwellings,  and  beyond  the  possibility  of 
doing  harm.  It  is  the  plan  which  your  Commission  recommend  for 
Boston. 

On  Plate  III.  is  reproduced  a  portion  of  the  plan  accompany- 
ing the  report  of  the  commission.  The  plan  shows  the  routes 
of  the  main,  intercepting,  and  outfall  sewers  recommended,  and 
the  proposed  locations  of  the  pumping-stations,  reservoirs,  and 
outlets.  It  will  be  seen  that  two  main  drainage  systems  were 
proposed,  one  for  each  side  of  the  Charles  River ;  that  on  the 
south  side  having  its  outlet  at  Moon  Island  and  that  on  the 
north  side  discharging  at  Shirley  Gut. 

The  former  system  was  designed  to  collect  and  carry  off  the 
sewage  from  all  of  Boston  south  of  Charles  River  and  from 
Brookline  ;  the  latter  was  to  drain  the  Charlestown  and  East 
Boston  districts,  and  also  the  neighboring  cities  of  Cambridge, 
Somerville,  and  Chelsea.  The  two  systems  were  identical  in 
their  general  features.  These  were  :  intercepting  sewers  along 
the  margins  of  the  city  to  receive  the  flow  from  the  already 
existing  sewers  ;  main  sewers  into  which  the  former  were  to 
empty  and  by  which  the  sewage  was  to  be  conducted  to  pump- 
ing-stations ;  pumping  machinery  to  raise  the  sewage  about  35 


Plate  III. 


MOVEMENTS    FOR   REFORM-COMMISSION   OF    1875.  19 

feet ;  outfall  sewers  leading  from  the  pumping-stations  to  reser- 
voirs near  the  points  of  discharge  at  the  sea-coast,  from  which 
reservoirs  the  sewage,  accumulated  during  the  latter  part  of 
ebb  and  the  whole  of  flood  tide,  was  to  be  let  out  into  the  har- 
bor during  the  first  two  hours  of  ebb-tide. 

The  cost  of  the  proposed  main  drainage  works,  as  estimated 
by  the  commission  in  its  report,  was  :  — 

For  the  territory  south  of  Charles  River      .     .     $3,746,500 
north  "  .     .       2,804,564 


Total $6,551,064 

The  commissioners'  recommendation  met  with  very  general 
acceptance.  But,  as  was  to  be  expected,  a  certain  amount  of 
opposition  to  it  was  encountered. 

One  remonstrance  against  the  adoption  of  the  proposed  plan, 
which  was  presented  to  the  City  Council  by  a  number  of  esti- 
mable citizens,  may  be  of  sufficient  interest  to  cite,  because  it  is  a 
type  of  the  kind  of  objections  which  are  often  urged  against 
plans  for  municipal  improvement,  however  carefully  considered 
by  the  most  competent  experts  :  — 

The  undersigned  resj)ectfully  remonstrate  against  the  adoption  of  the 
system  of  sewerage  proposed  in  Report  No.  3  of  this  year.  We  believe  if 
carried  into  execution  it  will  prove  not  only  ineffectual,  but  destructive  to 

the  health  and  prosperity  of  the  city Of  late  years  the  cost 

of  many,  if  not  most,  of  the  public  works  has  greatly  exceeded  the  esti- 
mates ;  in  some  instances,  it  is  said,  two  or  three  hundred  per  cent. 

Shou-ld  this  new  system  exceed  the  estimates  to  a  like  extent,  the  amount 
would  be  augmented  to  between  fifteen  and  twenty  millions  of  dollars.    .    . 

But  we  do  not  believe  it  (flushing)  will,  or  even  can,  be  made  to  per- 
form that  end  in  an  effective  or  satisfactory  manner ;  because  we  under- 
stand, by  the  report,  that  the  inclinations  of  the  sewers  will  afford  a  flow  at 
a  minimum  rate  of  only  two  miles  an  hour,  so  that  it  will  be  almost  impos- 
sible to  i:)revent  the  glutinous  slime  and  putrefactions  from  constantly  gath- 
ering and  adhering  more  or  less  to  the  sides  and  bottoms  of  the  sewers 
and  drains,  and  as  constantly  exhaling  the  deadly  gases  on  every  side. 
.  .  .  .  It  will  likewise  be  borne  in  mind  that  the  thick  mass  of  liquid 
corruption  within  the  sewers  and  drains  must  be  drawn  along  to  their  up- 
hill or  final  ascent  of  thirty  feet  and  over,  and  kept  in  motion  and  delivered 
at  the  distant  outlets  on  the  bay,  by  means  of  enormous  pumps  and  ma- 
chineiy  worked  by  steam-engines,     ....     for  a  stoppage  in  the  ojjer- 


20  MAIN    DRAINAGE    WORKS. 

ations  of  such  an  extensive  system  for  only  a  clay  or  two,  along  the  low 
lands  and  other  parts  of  the  city,  would  almost  inevitably  result  in  serious 

maladies  and  other  evil  consequences Will  not  the  exhalation 

and  odor  (from  the  storage  reservoirs)  blown  by  every  changing  wind  here 
and  there  along  the  wharves,  upon  the  shipping  and  back  upon  the  land, 
create  a  nuisance  so  offensive  and  unhealthful  as  to  become  intolerable  ?  No 
provision  seems  to  be  devised  to  prevent  such  emanations  or  their  baleful 
consequences.  In  these  noisome  reservoirs  the  contents  must  ever  be  ex- 
posed to  the  sun,  the  storms,  and  the  inclemency  of  the  weather. 

In  the  severity  of  winter  they  must  become  as  frozen  as  the  water  in 
the  bay  or  along  the  shores ;  and  as  often  as  they  are  converted  into  ice 
there  must  be  an  entire  stoppage  of  the  works.  .  .  .  Such  reservoirs  and 
outlets  might  be  reduced  to  ruins  in  any  future  day  of  hostilities  —  either 
foreio-n  or  domestic —  should  such  hostilities  ever  occur,  the  effect  of  which 
ruins  would  be  the  fatalities  of  the  plague 

There  is  now  but  a  single  system  before  the  authorities,  although  there 
are  not  less  than  five  different  systems  in  Europe  alone.  .  .  .  It  is  hereby 
requested  that  the  same  be  postponed,  and  that  a  reward  be  offered  for  the 
best  plan  for  sewerage  relief  ....  and  that  such  plans  be  referred  to 
a  commission  of  citizens  .  .  ...  with  power  to  give  the  reward  for  the 
best  plan. 

Other  remonstrants  thought  that  city  sewage  had  a  great 
manurial  value,  and  should  be  so  utilized  as  to  be  a  source  of 
revenue ;  still  others  considered  the  proposed  scheme  extrava- 
gant, and  advised  temporary  palliative  measures. 

What  prevented  these  remonstrances  from  having  much 
weight,  was  that  while  criticising  the  proposed  scheme,  they 
either  suggested  no  alternative  plan,  or  else  failed  to  show  that 
the  method  which  they  themselves  recommended  would  remedy 
the  existing  evils. 

As  a  compromise  the  City  Council  inclined  to  adopt  the 
recommendations  of  the  commission  in  so  far  as  they  referred 
to  the  territory  South  of  Charles  River,  which  included  those 
portions  of  the  city  which  suffered  most  from  inefiective  sewer- 
age. Application  was  made  to  the  Legislature  for  authority  to 
construct  works  in  general  accordance  with  the  recommendations 
of  the  Commissioners,  and  an  act,  approved  April  11,  1876, 
entitled  "  An  Act  to  empower  the  City  of  Boston  to  lay  and 
maintain  a  main  sewer  discharging  at  Moon  Island  in  Boston 
Harbor,  and  for  other  purposes,"  was  passed. 

The  subject  had  been  referred  by  the  City  Council  to  a  Joint 


MOVEMENTS    FOR   REFORM   COMMISSION    OF    1875.  21 

Special  Committee  on  Improved  Sewerage,  and  in  June,  1876, 
this  committee  reported,  recommending  the  adoption  of  the 
system  devised  by  the  commission,  and  that  surveys  and  esti- 
mates be  made  for  the  work,  and  also  that  the  feasibility  of  an 
outlet  at  Castle  Island  be  considered. 

By  an  order  approved  July  17, 1876,  the  sum  of  $40,000  was 
appropriated  for  the  purpose  of  making  surveys  and  of  procur- 
ing estimates  for  an  improved  system  of  sewerage  for  the  City 
of  Boston,  on  a  line  from  Tremont  Street  to  Moon  Island,  and 
also  on  a  line  from  said  street  to  deep  water  east  of  Castle 
Island. 

A  few  days  later  the  City  Engineer,  Mr.  Joseph  P.  Davis, 
appointed  the  writer  principal  assistant,  in  immediate  charge 
of  the  survev  and  investio-ations,  which  were  at  once  begun. 


22  MAIN    DRAINAGE    WORKS. 


CHAPTER  IV. 

PRELIMINARY   INVESTIGATIONS. 

By  a  liberal  interpretation  of  the  order  in  compliance  with 
which  the  survey  was  carried  on,  it  was  assumed  that  any 
information  was  desired  which  might  be  of  use  in  designing 
main  drainage  works,  in  general  accordance  with  the  plan 
recommended  by  the  commission. 

As  the  location  of  the  outlet  would  affect  materially  the 
whole  scheme  its  consideration  received  the  earliest  attention. 
It  was  necessary  that  the  discharge  should  be  into  favorable 
currents,  and  also  near  a  practicable  site  for  a  reservoir  which 
could  be  reached  by  the  outfall  sewer  from  the  city.  A  party 
for  hydrographic  work  was  organized,  consisting  of  one  assist- 
ant engineer,  one  additional  observer,  two  sailing-masters, 
and  two  boatmen.  Their  outfit  included  a  small  yacht  and  two 
tenders. 

A  projection  of  the  harbor  was  first  made,  and  the  triangula- 
tion  points  given  by  U.S.  Coast  Survey  were  plotted  upon  it, 
together  with  others  obtained  by  ourselves  from  these,  by 
means  of  the  plane  table  ;  the  shore  line  being  taken  from  a 
chart  belonging  to  the  Harbor  Commissioners.  A  sufiicient  num- 
ber of  prominent  points  having  been  determined  in  this  way,  it 
was  easy  at  any  time  to  locate  the  position  of  a  float  by  the  sex- 
tant. At  night,  when  other  objects  could  not  be  seen,  the  har- 
bor lights  furnished  points  for  observation. 

Some  difiSculty  was  experienced  in  deciding  upon  the  best 
form  of  float.  That  first  adopted  consisted  of  four  radiating 
arms,  with  canvas  wings  projecting  downward  from  them  (Plate 
IV.,  Fig.  4).  Upon  calm  days  this  form  indicated  very  fairly 
the  surface  velocit}'' ;  but  was  too  easily  influenced  by  winds 
and  waves  to  be  used  in  windy  weather,  as  it  then  invariably 
grounded  on  a  lee  shore. 

A  "surface  and  sub-surface  "  can-float  (Plate  IV.,  Fig.  5)  was 


Plate  IV. 


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niiii'iiivV  fir 


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PRELIMINARY   INVESTIGATIONS.  23 

used  somewhat,  and  gave  better  results  ;  but  an  ordinary  pole- 
float  (Plate  IV.,  Fig.  6),  about  14  feet  long  and  4  inches  in 
diameter,  was  finally  found  to  be  the  most  satisfactory,  indicat- 
ing the  mean  current,  which  often  differed  both  in  direction  and 
velocity  from  the  surface  current.  This  float  supported  a  flag, 
or  lantern,  and,  when  there  was  danger  of  its  grounding,  a 
shorter  one  was  substituted  for  it. 

In  all,  about  50  "  free-float "  experiments  were  made  upon 
the  currents  in  the  vicinity  of  Moon,  Castle,  Thompson's,  and 
Spectacle  Islands.  The  trips  varied  in  duration  from  6  hours, 
or  one  ebb-tide,  to  52  hours.  Angles  to  determine  the  posi- 
tion of  the  float  were  taken  each  half-hour,  and  were  re- 
corded together  with  the  direction  and  force  of  the  wind  and 
other  data.  During  observations  a  man  was  stationed  at  a  tide- 
o-au^e,  and  all  velocities  were  reduced  to  a  mean  rise  and  fall 
of  ten  feet.  The  results  obtained  from  the  float  experiments, 
stated  briefly,  were  as  follows  :  — 

Favorable  ebb  currents  were  found  to  pass  both  Moon  and 
Castle  Islands.  'That  passing  Spectacle  Island  was  sufficient  in 
strength,  but  unsuitable,  owing  to  its  direction  and  some  other 
characteristics ;  while  that  skirting  Thompson's  Island  was  alto- 
gether unfavorable.  Floats  leaving  the  vicinity  of  Moon  Island 
with  the  early  ebb  would  travel  seawards  with  an  average 
velocity  of  .74  miles  an  hour,  passing  between  Rainsford  and 
Long  Islands,  through  Black  Rock  Channel,  and  at  the  turn  of 
tide  would  reach  a  position  between  the  Brewsters  and  George's 
Island  about  four  miles  from  the  point  of  starting.  This  course 
is,  for  its  whole  extent,  outside  of  the  inner  harbor.  Floats  from 
Castle  Island  followed  Main  Ship  Channel  and  Broad  Sound, 
and  travelled  about  as  far  as  those  from  Moon  Island.  Return- 
ins^  with  the  flood-tide  the  floats  would  travel  about  two  miles 
towards  the  city,  and  with  the  succeeding  ebb  would  once  more 
move  seaward,  not  again  to  enter  the  harbor. 

Sewage,  being  fresh  water,  remains  for  a  while  at  least  upon 
the  top  of  the  denser  sea-water,  and  is  more  affected  by  surface 
currents  than  by  deeper  ones.  An  attempt,  more  interesting 
than  practically  instructive,  was  made  to  ascertain  to  what  ex- 
tent sewage  put  into  Boston  Harbor  would  be  difi'used  within 


24  MAIN    DRAINAGE    WORKS. 

a  few  days.  Fifty  bottle's  were  put  into  the  water  at  Moon 
Island,  each  containing  a  postal  card,  which  the  finder  was  re- 
quested to  mail,  stating  when  and  where  it  was  found.  Ten  of 
these  bottles  were  picked  up  within  the  next  three  weeks.  One 
of  them  was  found  at  Marshfield,  about  25  miles  south  of  its 
starting-point ;  another  at  Salem,  about  the  same  distance 
north ;  a  third,  30  miles  south-east  of  Cape  Ann,  and  the  re- 
maining seven  outside  of  Cape  Cod,  near  Provincetown,  Well- 
fleet,  and  Chatham,  from  50  to  80  miles  distant. 

Castle  island  would  have  been  much  more  easily  accessible 
from  the  city  than  Moon  Island,  but  its  selection  involved  sev- 
eral serious  disadvantages.  It  belongs  to  the  United  States, 
and  is  the  site  of  Fort  Independence.  Although  this  old  fort 
is  of  little  practical  value,  there  were  no  reasonable  grounds 
for  hope  that  the  government  would  permit  a  storage  reservoir 
to  be  located  on  the  island.  It  would  have  been  necessary  to 
place  that  structure  on  the  main  land  in  South  Boston.  The 
area  available  for  the  purpose  would  have  been  restricted  on 
account  of  its  great  cost.  Even  if  the  works  could  have  been 
so  constructed  as  to  be  wholly  inoffensive,  the  natural  prejudice 
in  the  community  against  the  proximity  of  sewage  would  have 
caused  great  opposition  to  the  building  of  a  reservoir  so  near 
to  a  densely  populated  district.  Moon  Island,  on  the  contrary, 
afforded  an  excellent  site  for  a  reservoir.  The  neighboring 
country  is  sparsely  settled,  and  there  is  no  dwelling  within  a 
mile  of  the  works.  The  outlet,  therefore,  was  finally  located 
at  this  point. 

The  next  problems  considered  were  the  selection  of  a  route 
for  the  outfall  sewer  between  the  city  and  Moon  Island  and  the 
location  of  the  pumping-station.  As  any  route  would  neces- 
sarily cross  a  portion  of  the  harbor  near  the  mouth  of  Neponset 
River,  it  was  thought  best  to  explore  the  nature  of  the  ground 
underlying  the  harbor  in  that  vicinity.  To  this  end  a  number 
of  artesian  borings  were  made  from  a  scow  fitted  for  the  pur- 
pose. Five-inch  or  smaller  gas-pipe  was  driven  to  the  required 
depth,  varying  from  20  to  100  feet,  and  the  earth  excavated 
from  within  them.  In  all,  139  such  borings  were  made. 
Those  on  the  line  selected  by  the  commissioners,  between  Fox 


CITY  OF  BOSTON, 

MAIN    DRAINAGE. 

PLAN  SHOWING 


AIN,  INTERCEPTING  &OUTFALL  SEWERS///^/    ^^ 

Aisin  [[{(' 

9     '^     y-^  yz"        %.  I  MILE  V^-- -_ , ,  ,.„  ,.„„ , 


PRELIMINARY    INVESTIGATIONS.  25 

Point  and  Squantimi  Beach,  showed  deep  beds  of  mud  under- 
laid by  sand  and  gravel ;  so  that  any  method  of  crossing  at  that 
point  would  have  been  difficult  and  expensive.  Moreover  Fox 
Point  Avas  thought  to  be  too  near  to  the  valuable  residence 
property  of  Savin  Hill  to  make  it  a  suitable  place  for  a  pump- 
ing-station.  Borings  at  the  mouth  of  the  river  opposite  Com- 
mercial Point  also  found  deep  beds  of  mud,  but  the  crossing 
being  much  shorter,  it  would  have  been  comparatively  easy  to 
have  constructed  a  stable  siphon  on  that  line.  Commercial 
Point  itself  was  a  fairly  good  site  for  a  puraping-station,  but 
would  have  been  somewhat  difficult  of  access  from  the  city. 
Ground  suitable  for  tunnelling  was  discovered  between  Old 
Harbor  Point  and  Squantum  Neck.  This  was  the  most  direct 
line  from  the  city  to  Moon  Island,  and  comparative  estimates 
showed  it  to  be  also  the  cheapest  line.  Its  chief  merit,  however, 
which  caused  it  to  be  selected,  was  that  it  permitted  the  use  of 
Old  Harbor  Point  as  a  site  for  the  pum ping-station.  This 
point  comprises  over  100  acres  of  marsh  land,  valued  by 
the  city  assessors  at  only  $200  an  acre.  It  is  itself  destitute 
of  habitations,  and  sufficiently  remote  from  any  to  afford  assur- 
ance that  operations  carried  on  there  will  not  be  a  source  of 
offence. 

Before  adopting  the  tunnel  line  a  plan  was  considered  by 
which  the  sewage,  instead  of  being  raised  at  Old  Harbor  Point, 
was  to  flow  thence  by  gravitation  to  a  pumping-station  at  Moon 
Island,  on  a  nearlj^  direct  line  between  the  two  points.  The 
sewer  was  to  be  built  above  oround  and  sunk  into  a  trench  dugf 
to  an  even  grade  in  the  bottom  of  the  harbor.  To  determine 
the  feasibility  of  this  plan  borings  were  made  to  test  the 
nature  of  the  ground  on  the  proposed  line.  The  character  of 
the  ground  developed  by  these  borings  was  not  considered  very 
favorable,  and  a  decision  of  the  Harl)or  Commissioners  requir- 
ing the  sewer  to  he  placed  lower  than  was  considered  practi- 
cable caused  the  proposed  plan  to  be  abandoned. 

Having  decided  to  locate  the  pumping-station  at  Old  Harbor 
Point  the  routes  of  the  main  and  intercepting  sewers  were 
next  selected.  The  peculiar  geological  formation  of  the  region 
about  Boston,  causing  frequent  elevation  of  the  bed-rock,  not 


26  MAIN    DEAINAGE    WORKS. 

always  shown  by  surface  indications,  and  the  sometimes  un- 
suspected presence  of  deep  beds  of  marsh  mud,  rendered  it 
necessary  to  test  carefully  the  nature  of  the  ground  through 
which  it  was  proposed  to  build  the  sewers,  since  its  character 
would  form  such  an  important  element  in  their  cost  and  sta- 
bility. The  slowness  and  expense  of  artesian  methods  of 
boring  precluded  their  use.  Light  auger-rods  were  therefore 
constructed,  and  it  was  found  that  by  them  the  character  of  the 
ground  could  be  ascertained  with  approximate  accuracy  and 
with  little  expense  or  delay.  These  tools,  and  the  manner  of 
using  them,  are  shown  on  Plate  IV.,  Figs.  1  to  3.  Including 
work  done  before  and  after  the  beginning  of  construction,  more 
than  30,000  lineal  feet  of  borings  were  thus  made,  at  an  average 
cost  of  about  25  cents  per  foot. 

There  was  no  trustworthy  information  extant  concerning  the 
position  and  condition  of  the  city  sewers  which  were  to  be  inter- 
cepted. Careful  surveys  were  therefore  made,  of  about  50 
miles  in  extent,  of  such  sewers  as  were  in  the  vicinity  of  the 
proposed  intercepting  sewers.  Plans  and  profiles  of  these 
were  made,  with  cross-sections  and  such  details  of  construction 
as  could  be  ascertained. 

Nearly  all  buildings  in  the  Back-Bay  and  South-End  districts 
of  the  city  are  supported  on  piles.  By  city  ordinance  the  tops 
of  the  piles  are  not  to  be  higher  than  Grade  5,  or  mid-tide 
level ;  in  fact  many  of  them  are  a  foot  or  tw^o  higher.  Fears 
were  expressed  that  the  intercepting  system  (by  doing  away 
with  the  semi-daily  damming  up  by  the  tide  of  the  contents 
of  the  sewers)  might  lower  considerably  the  soil-water  in  such 
regions,  and,  by  reducing  it  below  the  tops  of  the  piles  cause 
them  to  decay  and  endanger  the  stability  of  the  buildings  sup- 
ported by  them. 

To  see  if  such  danger  was  to  be  apprehended,  it  was  decided 
to  produce  in  one  of  the  Back-Bay  sewers  the  precise  condition 
which  would  exist  if  the  new  system  was  constructed,  and  to 
notice  the  effect  upon  the  soil-water.  To  this  end  a  steam 
pump  w^as  put  into  the  Berkeley-Street  sewer  near  the  outlet 
and  by  continual  pumping  (except  at  low  tide)  the  sewage 
was  kept  but  a  few  inches  deep,  as  it  would  be  if  discharging 


PRELIMINAEY   INVESTIGATIONS.  27 

into  an  intercepting  sewer.  Previously  20  pipes  had  been 
driven  below  the  surface  of  soil-water  ;  some  within  a  few  feet 
of  the  sewers,  others  a  few  hundred  feet  away,  and  still  others 
several  blocks  distant.  The  height  of  the  soil-water  standing 
in  each  pipe  was  measured  twice  each  day  during  the  continu- 
ance of  the  pumping. 

The  method  of  making  these  measurements  was  ingenious, 
and  perhaps  novel.  The  elevation  of  the  top  of  each  pipe  was 
known,  and  the  distance  from  the  top  to  the  surface  of  water 
was  taken  with  a  steel  tape.  To  the  bottom  of  the  tape  was 
attached  a  lead  weight,  with  a  needle  fixed  in  its  top  so  adjusted 
that  the  point  of  the  needle  was  just  opposite  to  the  end  of  the 
tape.  A  small  bit  of  metallic  potassium  was  put  on  the  point 
of  the  needle.  The  instant  this  touched  the  water  it  ignited 
explosively,  and  the  flash  and  sound  could  be  easily  distin- 
guished from  above.  A  sketch  of  the  apparatus  is  shown  by 
Fig.  7,  Plate  IV. 

It  was  found  that  the  surface  of  the  soil-water  was  nearly 
level  over  the  whole  Back-Bay  district,  averaging  7.7  feet 
above  mean  low  water,  and  its  height,  while  slightly  affected 
by  local  contours  of  the  surface,  was  independent  of  the  sewers 
in  its  vicinity.  For  instance,  the  water  in  the  vicinity  of  the 
Dartmouth-Street  sewer  was  at  the  same  level  as  that  near  the 
Berkeley-Street  sewer,  although  the  latter  sewer  is  two  feet 
lower  than  the  former.  Also  it  was  found  that  the  soil-water 
rose  and  fell,  responding  quickly  to  any  rain  or  melting  of 
snow  (the  extreme  rise  due  to  four  inches  of  surface-water  being 
one  foot) ,  and  that  the  variation  was  nearly  uniform  over  the 
entire  district. 

Finally  it  appeared  that  the  pumping,  which  continued  53 
days,  afiected  but  slightly,  and  that  only  within  100  feet  of  the 
sewer,  the  soil-water  in  the  vicinity  of  Berkeley  Street.  At 
the  close  of  the  experiment,  the  sewer  resuming  its  former 
conditions,  the  soil-water  in  its  immediate  vicinity  rose  from 
an  inch  to  an  inch  and  one-half,  and  thereafter  fluctuated  in 
unison  with  the  water  in  other  localities. 

The  experiment  was  thought  to  show  that  no  dangerous  low- 


28  MAIN    DRAINAGE    WOEKS. 

ering  of  the  ground-water  need  be  apprehended  in  consequence 
of  the  adoption  of  an  intercepting  system. 

The  following  was  the  general  basis  of  calculations  for 
amounts  of  sewage  and  sizes  of  sewers.  It  was  necessary  to 
assume  some  limit  to  the  territory  which  should  be  tributary 
to  the  intercepting  system.  A  natural  limit  in  this  case  seemed 
to  be  afforded  by  the  Charles  and  Neponset  Rivers,  which,  with 
Mother  Brook  connecting  them,  include  an  area  of  about  58  square 
miles.  Of  this  area  about  46  square  miles  is  high  land,  40  or 
more  feet  above  low  water,  and,  as  suggested  by  the  com- 
missioners, drainage  from  districts  above  Grade  40  could,  if 
necessary,  be  intercepted  by  a  "high-level"  intercepting  sewer 
and  could  flow  by  gravitation  to  the  reservoir  at  Moon  Island. 
There  remain  12  square  miles  below  Grade  40  which  must 
forever  drain  into  the  "  low-level"  system.  As,  however,  it  will 
be  long  before  the  high-level  sewer  is  built,  and  in  the  mean 
time  sewers  from  areas  above  Grade  40  must  connect  with  the 
low-level  system,  for  purposes  of  calculation,  it  was  assumed 
that  20  squkre  miles  would  be  tributary  to  the  proposed  sys- 
tem. 

The  prospective  population  was  estimated  at  an  average  of 
62|-  persons  to  each  acre,  or  800,000  in  all.  This  estimate  of 
62^  persons  to  the  acre  was  used  in  calculations  affecting  the 
main  sewer ;  but  in  proportioning  branch  intercepting  sewers 
greater  densities  of  population  were  assumed,  to  provide  for 
possible  movements  of  population.  The  amount  of  sewage  per 
individual  was  estimated  at  75  gallons,  or  10  cubic  feet,  in  each 
24  hours.  The  maximum  flow  of  sewage  per  second  was  esti- 
mated at  one  and  one-half  times  the  average  flow  due  to  10 
cubic  feet  per  day. 

On  this  basis  the  maximum  flow  of    sewage-proper  to  be 

provided  for  would  be  ^?^'^!?a  ^  I-a  X  1.5  =  138.88  cubic  feet 
^  24  X  60  X  bO 

per  second. 

This  amount  was  nearly  doubled  by  adding  to  it  100  cubic 
feet  per  second  as  a  provision  for  rain-water.  This  would  rep- 
resent a  little  less  than  one-fourth  inch  of  rainfall  in  24  hours, 
per  acre  of  tributary  area ;  but  it  was  intended,  in  practice,  to 


PRELIMINARY    INVESTIGATIONS.  29 

admit  little,  if  any,  rain  from  regions  where  the  cellai-s  were 
not  subject  to  flooding,  and  reserve  the  full  capacity  of  the 
sewers  and  pumps  to  relieve  certain  low  districts  where  the 
cellars  are  generally  much  below  high  tide,  and  were  often 
partly  filled  with  water  in  time  of  rain. 

For  purposes  of  calculation,  therefore,  the  prospective  maxi- 
mum flow  per  second  in  the  main  sewer  was  assumed  to  be 
138.88  -|-  100  =  238.88  cubic  feet  per  second.  The  inclination 
of  the  sewer  was  1  in  2,500,  and  it  was  designed  (as  were  all 
of  the  sewers)  to  flow  about  half  full  with  its  calculated  maxi- 
mum amount  of  sewage.  Although  this  rule  required  that  the 
sewers  should  be  larger  than  they  would  be  if  designed  to  flow 
full,  it  was  adopted  because  it  gave  about  three  feet  less  depth  of 
excavation  for  the  whole  sewer  system,  saved  three  feet  lift  in 
pumping,  provided  storage-room  for  large  additional  amount* 
of  sewage  due  to  intermission  of  pumping  or  to  rain,  and 
afibrded  more  head-room  to  workmen  entering  the  sewers. 

In  designing  the  smaller  intercepting  sewers  the  method  em- 
ployed was  somewhat  as  follows  :  the  districts  drained  by  the 
several  city  sewers  were  ascertained,  and  their  respective  areas 
in  acres  were  calculated.  The  largest  population  which  by  any 
chance  might  live  on  these  areas  in  the  future  was  estimated, 
i.e.,  guessed.  The  future  average  amount  of  sewage  proper 
due  to  such  population  was  doubled  for  safety,  and  an  addi- 
tional amount  added  for  rain,  usually  equalling  that  from  .25- 
inch  rainfall  in  24  hours.  If  an  intercepting  sewer  large  enough 
to  carry  this  total  amount  when  flowing  half  full  would  have 
been  too  small  to  be  entered  conveniently,  its  size,  or  sometimes 
only  its  height,  was  increased  sufiiciently  to  aftbrd  convenient 
head-room. 

Velocities  of  flow  were  calculated  by  the  formula  V  =  C  VRI, 
with  Mr.  Kutters  coefficients,  obtained  by  using  .013  as  the 
coefficient  for  roughness. 

During  the  early  stages  of  the  work,  the  City  Engineer,  Mr. 
Davis,  made  a  trip  to  Europe  to  examine  the  foreign  sewerage 
works  of  best  repute.  Information  was  thus  gained  which  was 
used  in  designing  the  Boston  works. 

In  July,  1877,  the  City  Engineer  reported  the  results  of  his 


30  MAIN    DRAINAGE    WORKS. 

preliminary  survey,  and  on  August  9  of  the  same  year  orders 
of  the  City  Council  were  approved,  authorizing,  and  making  an 
appropriation  for,  the  construction  of  an  improved  system  of 
sewerage,  in  general  accordance  with  the  proposed  plan,  under 
authority  of  the  Act  of  Legislature. 

The  City  Council  committed  the  charge  of  building  the  Main 
Drainage  Works  to  a  Joint  Special  Committee  on  Improved 
Sewerage,  consisting  of  three  Aldermen,  and  five  mem1)ers  of 
the  Common  Council.  This  committee  changed  its  member- 
ship  every  year  except  when  one  or  more  of  its  members  were 
reelected  and  were  again  appointed  on  it.  By  city  ordinance 
all  engineering  works  are  built  by  the  City  Engineer.  The 
Main  Drainage  Works,  therefore,  were  constructed  under  the 
direction  of  Mr.  Joseph  P.  Davis,  C.E.,  City  Engineer,  until 
his  resignation  in  1880,  and  since  that  date  by  his  successor  in 
office,  Mr.  Henry  M.  Wightman,  CE.^ 

^  Since  the  above  was  written  the  city  has  sustained  a  great  loss  in  the  death  of  Mr. 
Wightman.    Mr.  WilHam  Jackson  has  been  elected  City  Engineer. 


MAIN    SEWEB.  31 


CHAPTEE    V. 

MAIN    SEWER. 

The  main  sewer  is  about  3i  miles  long,  and  extends  from  the 
pumping-station  at  Old  Harbor  Point  to  the  junction  of  Hunt- 
ington Avenue  and  Camden  Street.  Its  inclination  throughout 
its  whole  extent  is  1  foot  vertical  in  2,500  horizontal.  At 
the  pumping-station  the  water-line  of  the  invert,  i.e.,  its  bot- 
tom, is  about  14  feet  below  the  elevation  of  mean  low  tide.  From 
this  point,  in  its  course  towards  the  city,  the  sewer  passes  for 
about  a  mile  across  the  Calf  Pasture  Marsh,  so  called.  The 
surface  of  this  marsh  is  about  six  inches  above  mean  high  water, 
and,  the  mean  rise  and  fall  of  the  tide  being  ten  feet,  the  aver- 
age depth  of  excavation  required  for  this  section  of  work  was  24 
feet.  Up  to  the  junction  of  the  South  Boston  intercepting 
sewer  the  main  sewer  is  ten  feet  six  inches  in  diameter.  It  was 
founded  sometimes  upon  clay  and  sometimes  upon  sand. 
Figs.  1  and  2,  Plate  VI.,  show  the  usual  methods  of  construc- 
tion. Eubble  side  walls  were  built  for  the  greater  portion  of  the 
distance.     Fig.  3  shows  the  bond  used  in  the  spandrels. 

On  this  section  occurred  the  only  case  during  the  construction 
of  the  entire  Main  Drainage  Works  in  which  a  sewer  was 
broken  so  that  a  portion  of  it  had  to  be  taken  down  and  rebuilt. 
At  one  point,  for  a  distance  of  150  feet,  the  marsh  mud,  which 
usually  was  from  five  to  ten  feet  deep  below  the  surface  of  the 
ground,  came  down  below  the  spring-line  of  the  sewer.  Owing 
to  carelessness,  on  the  part  of  the  contractor,  in  back-filling 
around  the  haunches,  or  in  withdrawing  the  sheet  planks,  the 
sewer  spread  six  inches,  and  sank  correspondingly  at  the  crown. 
Fig.  4  shows  the  shape  assumed  at  the  point  of  maximum  dis- 
tortion. Although  even  this  portion  was  probably  stable,  it  was 
not  considered  wise  to  establish  a  precedent  of  accepting  any  im- 
perfect work.  Accordingly  the  trench  was  reopened,  the  sewer 
uncovered,  and  its  arch  broken  down  with  sledge  hammers. 


32  MAIN   DRAINAGE   WORKS. 

It  was  found  that  the  12-mch  Akron  drain-pipe  built  under 
the  sewer,  to  facilitate  drainag-e  of  the  trench  durino-  construe- 
tion,  was  broken  at  this  point,  and  the  water  from  it,  accumu- 
lated from  4,000  feet  of  trench,  found  an  outlet  and  poured 
over  the  side  walls  into  the  invert.  This  water  was  controlled 
by  pumps,  but  was  found  to  have  washed  out  a  quantity  of 
sand,  causing  a  considerable  cavity  under  the  sewer  platform. 
The  limits  of  the  cavity  having  been  determined,  five  holes, 
ten  feet  apart  on  centres,  were  made  through  the  bottom  of  the 
sewer  and  3-inch  wrought-iron  gas-pipes  were  inserted  into 
them.  Two  of  these  pipes  were  about  30  feet  long  and  three 
others,  for  vents,  were  five  feet  long.  Constant  streams  of 
grout,  made  from  47  casks  of  neat,  quick-setting  Portland  ce- 
ment, were  forced  under  a  25-foot  head,  through  the  long  pipes 
into  the  cavity  until  it  was  filled,  as  proved  by  the  cement  ris- 
ing in  the  short  pipes.  The  grout  hardened  and  furnished  a 
secure  foundation.  Special  ribs  were  cut  to  fit  the  invert,  which 
was  again  arched  over  and  the  trench  refilled. 

Figs.  5  and  6,  Plate  VI.,  show  methods  of  connecting  man- 
holes with  the  main  sewer.  These  structures  are  about  400 
feet  apart,  and  are  placed  alternately  on  one  side  of  and  over 
the  centre  of  the  sewer.  At  man-holes  the  arch  is  supported 
by  cut-granite  skewback  stones.  At  the  top  of  the  man-holes 
are  cast-iron  frames  supporting  circular  iron  covers.  The  cov- 
ers are  perforated  for  purposes  of  ventilation.  The  holes  are 
quite  large,  so  that  they  are  not  liable  to  become  stopped  up. 
They  also  taper  considerably,  being  larger  below  than  they  are 
on  top.  To  prevent  road  detritus  and  miscellaneous  rubbish 
from  falling  into  the  sewers,  catch-pails  are  suspended  below 
the  covers  to  receive  whatever  may  fall  through  the  holes.  The 
pails  are  of  galvanized  iron,  well  coated  with  tar.  They  can  be 
lifted  out,  emptied,  and  replaced,  as  occasion  demands. 
Wrought-iron  steps  were  built  into  the  man-holes  during 
construction.  These  details  are  shown  on  Plate  VI.,  Figs. 
7  and  8. 

Above  the  point  where  the  South  Boston  intercepting  sew- 
ers join  the  main  sewer  the  latter  is  nine  feet  in  diameter.  For 
about  half  a  mile  the  ground  is  high,  but  a  location  through 


Plate  VI. 


SIDE    ENTRANCE  AND  BOAT  CHAMBER 


Fi.^.  16 


COVER 


MAIN    SEWER.  33 

it  could  not  be  avoided  without  making  a  considerable  detour. 
For  1,900  feet,  in  Mount  Vernon  Street,  the  sewer  was  built  by 
tunnelling  through  conglomerate  rock  and  coarse  sand.  The 
rock,  where  it  surrounded  the  tunnel,  presented  no  serious  ob- 
stacle :  but  the  sand  tended  to  run  into  the  excavation,  and  re- 
quired close  sheeting  and  heavy  bracing  to  support  it.  Fig. 
9,  Plate  VI.,  shows  the  sewer  in  tunnel  on  this  section.  For 
several  hundred  feet  the  sewer  grade  was  near  the  surface  of 
the  ledge  and,  the  latter  being  very  irregular  and  covered  with 
boulders,  tunnelling  operations  were  attended  with  much  diffi- 
culty, and  several  caves  occurred.  For  a  length  of  160  feet 
the  ground  was  opened  from  the  top  and  the  sewer  was  built  in 
an  open  trench  about  45  feet  deep. 

The  sewer  in  the  tunnel  was  well  built,  but  after  completion, 
on  removing  the  pumps  so  that  the  water  table  in  the  vicinity 
was  permitted  to  rise  above  the  sewer,  the  latter  was  found  to 
leak  a  good  deal.  The  leaks,  however,  could  be  successfully 
calked.  The  process  consisted  in  raking  out  a  joint,  where  a 
leak  occurred,  to  the  full  depth  of  the  brick  and  driving  in 
sheet  lead  for  half  the  depth,  the  remainder  being  filled  with 
cement. 

Excepting  a  section  in  East  Chester  Park,  from  Clapp  Street 
to  Magazine  Street,  the  main  sewer  was  built  by  contract.  The 
laying,  out  as  a  street  of  East  Chester  Park,  east  of  Albany 
Street,  had  been  contemplated  by  the  authorities  for  some  time, 
and  action  to  that  end  was  taken  in  time  to  permit  the  sewer 
being  located  there.  The  borings  on  this  line  showed  that  there 
were  beds  of  mfa'sh  mud  between  Clapp  and  Magazine  Streets 
which  were  from  20  to  86  feet  deep  below  the  marsh  surface. 
As  it  would  have  been  difficult  to  build  a  stable  sewer  in  such 
ground,  and  impossible  to  prevent  one,  if  built,  being  destroyed 
when  the  street  should  be  filled  over  and  around  it,  it  was  de- 
cided to  fill  the  street  to  full  lines  and  grades  before  attempting 
to  build  the  sewer. 

A  contract  was  accordingly  concluded  by  which  the  street 
was  filled  with  gravel  brought  by  the  N.Y.  and  N.E.  Eailroad. 
So  great  was  the  settlement  of  this  filling  into  the  mud  that 
over  106,000  cubic  yards  of  gravel  were  required.     The  marsh 


34  MAIN    DRAINAGE.  WORKS. 

level  for  100,  or  more,  feet  on  either  side  of  the  filled 
street  was  pushed  up  by  the  filling  from  8  to  14  feet  high.  A 
surcharge,  20  feet  wide  on  top  and  eight  feet  high,  was  put 
upon  the  street,  west  of  the  N.Y.  &  N.E.  Eailroad,  where  the 
mud  was  deepest,  to  insure  prompt  settlement. 

Building  a  stable  sewer  in  a  street  so  recently  filled  being  a 
difficult  operation,  requiring  methods  of  treatment  which  can- 
not be  determined  upon  beforehand,  it  was  thought  best  to 
build  this  section  by  day's  labor. 

As  a  masonry  structure  would  have  been  broken  when  the 
trench  was  refilled,  a  wooden  sewer  was  adopted  (Fig.  10, 
Plate  YI. ) .  This  consisted  of  an  external  wooden  shell,  formed 
of  4-incli  spruce  plank,  ten  inches  wide,  every  fourth  plank 
being  wedge-shaped  ;  the  whole  securely  spiked  and  treenailed 
together  and  finally  lined  with  four  inches  of  brick  or  concrete 
masonry. 

The  depth  of  excavation  for  this  sewer  was  from  32  to  36 
feet,  and  the  pressures  were  so  great  as  to  require  very  heavy 
bracing.  As  many  as  60  braces  of  8  inch  X  8  inch,  or  heavier 
timber,  were  sometimes  used  for  a  length  of  18  lineal  feet  of 
trench ;  and  these,  when  taken  out,  were  all  found  to  be  either 
broken,  or  so  crippled  as  to  be  unfit  to  use  again.  Frequently 
the  earth  on  one  side  of  the  trench  was  found  to  be  diiferent 
from  that  on  the  other,  which  caused  very  unequal  pressures,  so 
that  internal  bracing  was  necessary  to  maintain  the  sewer  in  its 
proper  shape  until  the  trench  had  been  back-filled.  It  was 
found  necessary  to  build  the  shell  with  a  vertical  diameter 
four  inches  greater  than  was  required  for  the^tnasonry  lining, 
to  allow  for  settlement,  change  of  shape,  and  compression  of 
the  timber.  The  vertical  diameter  inside  of  the  lining  was  also 
increased,  so  that,  if  in  places  the  sewer  should  settle  as  a  whole, 
the  bottom  could  be  brought  to  the  true  grade,  and  still  leave 
the  established  sectional  area. 

The  length  of  this  section  was  1,894  feet.  Ground  was  first 
broken  in  August,  1879,  and  the  work  was  completed  in  Octo- 
ber, 1880.  For  excavating  and  back-filling  the  trench,  machin- 
ery designed  by  the  Superintendent,  Mr.  H.  A.  Carson,  was 
used.     The  average  cost  per  lineal  foot  of  the  completed  sewer 


MAIN    SEWER.  35 

was  $56.  For  severiil  hundred  feet,  where  the  mud  htid  been 
deepest,  a  continual  slight  shrinkage  and  settlement  of  the 
gravel  tilling  under  the  sewer  occurred  for  a  year  or  more. 
The  sewer  itself,  also,  settled  in  a  long  curve,  whose  greatest 
depth  below  the  original  grade  line  was  about  1(S  inches.  A 
masonry  sewer  would  have  been  broken  by  such  movement, 
but  the  wooden  one  having  consideralile  tlexibility  was  appar- 
ently uninjured.  At  present  (1885)  the  street  seems  to  have 
assumed  a  condition  of  permanent  stability. 

In  East  Chester  Park,  from  Magazine  Street  to  Albany 
Street,  clay  was  chiefly  encountered,  and  the  sewer  generally 
consisted  of  a  simple  ring  of  brick-work  without  side  walls,  and 
its  construction  presented  few  features  of  special  interest.  As 
a  precaution  in  passing  within  35  feet  of  a  large  gas-holder, 
tongued  and  grooved  4-inch  sheet  planks  were  driven,  and 
the  trench  was  back-filled  with  concrete  to  the  crown  of  the 
sewer  arch  (Fig.  11).  In  passing  across  the  old  Roxbury 
Canal,  which  had  been  recently  filled  by  the  city,  an  influx  of 
tide-water  alono-  the  loose  walls  of  the  canal  and  throuoh  the 
filling  occasioned  some'  delay  and  expense.  The  water  was 
finally  kept  out  by  double  rows  of  tongued  and  grooved  sheet- 
piling.  A  side  entrance  and  boat-chamber  (Fig.  12),  were  built 
on  this  section,  at  the  corner  of  Swett  Street.  The  latter 
structure  resembled  a  very  large  man-hole,  with  a  rectangular 
opening  from  the  street,  11X4  feet  in  dimensions.  This  was 
built  to  allow  the  lowerino-  of  boats  into  the  sewer. 

At  Albany  Street  the  east-side  intercepting  sew^er  joins  the 
main,  and  above  this  point  the  latter  is  again  reduced  in  size,  to 
eight  feet  three  inches  wide  by  eight  feet  five  inches  high.  The 
extra  horizontal  course  was  put  in  at  the  spring  line  because  it 
was  supposed  to  facilitate  dropping  and  moving  the  centres. 
In  East  Chester  Park,  and  Washington  Street  from  Albany  to 
Camden  Street,  the  sewer  was  built  chiefly  in  clay,  and  con- 
sisted of  a  ring  of  brick-work.  For  about  300  feet,  however, 
near  Albany  Street,  mud  was  found,  and  a  foundation,  consisting 
of  a  timber  platform  supported  on  piles,  became  necessary 
(Fig:  13,  Plate  VI.). 

In   Camden    Street,  from   Washington    Street   to   Tremont 


36  MAIN    DRAINAGE    WOEKS. 

Street,  a  distance  of  1,391  feet,  the  depth  of  trench  required 
would  have  been  26  feet.  Camden  Street  is  rather  narrow,  and 
contains  sewer,  gas,  and  water  pipes.  As  good  clay  was  found 
at  a  depth  five  or  more  feet  above  the  top  of  the  sewer,  it  was 
thought  that  it  would  be  as  cheap  to  the  city,  and  decidedly 
less  annoying  to  residents  on  the  street,  to  build  the  sewer  by 
tunnelling  beneath  the  surface  (Fig.  14).  Working  shafts  were 
sunk  about  250  feet  apart,  and  headings  in  each  direction  driven 
from  them.  At  one  or  two  points  the  miners  permitted  the 
roof  of  the  tunnel  to  settle  slightly,  by  which  the  common  sewer 
above  was  cracked,  and  some  trouble  caused  by  the  sewage 
leaking  into  the  tunnel.  The  main  sewer  was  back-filled  above 
the  arch  with  clay,  packed  in  under  the  lagging  as  firmly  as 
possible.  On  the  whole  the  method  of  construction  was  suc- 
cessful, and  a  well-built  sewer  was  obtained.  Its  cost  was 
$22.52  per  lineal  foot. 

At  Tremont  Street  the  Stony-Brook  intercepting  sewer  is 
taken  in.  At  this  point,  as  at  all  other  places  where  intercept- 
ing sewers  join  the  main  sewer,  the  grade  of  the  latter  rises 
abruptly  somewhat  less  than  a  foot,  or  enough  to  maintain  the 
established  inclination  on  the  surface  of  the  sewage  at  the  time 
of  maximum  How.  From  Tremont  Street  to  the  present  end  of 
the  main  sewer,  at  Huntington  Avenue,  the  sewer  was  built  in 
open  cut  (Fig.  15),  and  for  a  large  part  of  the  distance  needed 
side  walls  and  piling  for  its  support.  Just  west  of  the  B.  & 
P.  R.R.  another  boat-chamber  and  side  entrance  (Fig.  16) 
were  built,  and  a  third  side  entrance,  reached  by  a  stone  stair- 
way leading  from  the  sidewalk,  was  constructed  at  Huntington 
Avenue. 

The  total  cost  of  the  3.2  miles  of  main  sewer  was  $606,031 
being  an  average  of  $36.09  per  lineal  foot. 


INTERCEPTING    SEWERS.  37 


CHAPTER  VI. 

INTERCEPTING    SEWPiRS. 

As  before  stated,  and  as  shown  by  the  plan  (Plate  V.),  the 
South  Boston  intercepting  sewer  is  the  first  to-  join  the  main 
sewer  in  the  latter's  course  from  the  pumping-station  towards 
the  city  proper.  This  intercepting  sewer,  by  its  two  branches, 
is  intended  finally  to  encircle  the  peninsula  on  which  South 
Boston  is  situated,  and  intercept  the  sewage  flowing  in  the  com- 
mon sewers,  which  have  heretofore  discharged  their  contents  at 
nineteen  outlets,  in  the  immediate  vicinity  of  a  dense  popula- 
tion. 

At  the  point  of  junction  the  grade  of  the  intercepting  sewer 
is  1.5  feet  higher  than  that  of  the  main  sewer,  so  that  the  sew- 
age in  the  former  shall  not  be  dammed  back,  and  the  established 
rate  of  inclination  shall  be  maintained  on  the  surface  of  the 
sewage  in  both  sewers  at  the  time  of  maximum  discharge.  In 
all  cases  where  a  main-drainage  sewer  joins  another,  the  junc- 
tion is  made  at  a  "  bell-mouth  "  connection  chamber,  in  which 
the  axes  of  the  sewers  meet  by  lines  or  curves  tangent  to  each 
other,  so  that  the  two  currents  may  unite  with  the  least  dis- 
turbance to  either.  Sections  of  the  "  bell-mouth  "  junction  of 
the  two  branches  of  the  South  Boston  sewer,  at  Hyde  Street, 
are  shown  by  Fig.  14,  Plate  VII.  On  each  intercepting 
sewer,  just  before  it  reaches  the  main  sew^er,  is  built  a  penstock 
chamber,  containing  a  cast-ii'on  penstock  gate,  by  which  the 
flow  can  be  cut  ofi",  so  that  the  main  sewer  can  be  entirely 
emptied,  should  it  ever  be  desirable  to  do  so.  At  such  times 
the  city  sewage  would  be  discharged  at  the  old  outlets,  which 
are  all  retained  and  protected  by  tide-gates.  A  sketch  of  the 
penstock  on  the  South  Boston  sewer  is  given  by  Fig.  6. 

Up  to  where  it  divides  this  sewer  is  circular,  six  feet  in 
diameter.  The  average  depth  of  excavation  was  20  feet.  Clay 
or  sand  was  usually  found,  and  the  sewer  consists  of  a  simple 


38  MAIN    DRAINAGE    WORKS. 

ring  of  brick-work,  12  inches  thick,  though  for  about  350  feet, 
where  the  sand  was  wet  and  inclined  to  run,  abutment  walls  of 
rubble  masonry  were  used.  Figs.  12  and  13  show  cross- 
sections  of  this  sewer.  The  brick  invert  was  laid  with  Port- 
land cement  mortar,  one  part  cement  to  two  parts  sand,  and  the 
arch  was  laid  with  American  (Eosendale)  cement  mortar,  one 
part  cement  to  1.5  parts  sand.  This  was  the  common  practice 
in  building  the  main-drainage  sewers,  Portland  cement  being 
used  in  the  inverts,  on  account  of  its  greater  resistance  to  abra- 
sion. When  Rosendale  cement  was  used  for  building  inverts, 
the  proportion  required  was  equal  parts  of  cement  and  sand. 

The  inclination  of  this  sewer  throughout  the  greater  portion 
of  its  extent  is  1  in  2,000,  which  affords  a  velocity  of  flow 
sufficient  to  prevent  deposits  of  sludge,  but  not  sufficient  to 
keep  in  suspension  sand  and  road  detritus.  A  sharper  inclina- 
tion would  have  been  desirable  had  it  been  practicable  to  ob- 
tain one.  Few  of  the  main  drainage  sewers  have  a  greater 
inclination  than  1  in  2,000,  and  it  was  expected  from  the  first 
that  flushing  would  occasionally  be  required  to  prevent  the 
accumulation  of  deposits.  To  provide  for  this,  iron  flushing- 
gates  are  built  into  the  sewers  at  intervals  of  about  half  a  mile. 
The  first  flushing-gate  on  the  South  Boston  sewer  is  just  below 
the  fork  at  Hyde  Street.  A  sketch  of  this  gate  is  given  b}^ 
Fig.  15.  Usually  the  gate  stands  above  the  sewer,  in  the 
man-hole.  It  is  kept  vertical  by  two  small  stop-bolts  at  its  top. 
To  flush  the  sewer  the  gate  is  lowered  against  its  seat,  built 
into  the  bottom  of  the  sewer,  and  the  sewage  accumulates  be- 
hind it  as  deep  as  the  gate  is  high.  The  stops  are  then  with- 
drawn and  the  gate  raised  until  it  clears  its  lower  seat,  when  it 
tilts  over  into  a  horizontal  position  and  opens  a  free  passage 
for  the  dammed-up  sewage. 

The  greater  [)art  of  South  Boston  is  high  land,  and  there  are 
but  few  low  cellars  there  which  are  subject  during  rain-storms 
to  flooding  at  high  tide.  In  order  that  the  full  capacity  of  the 
sewers  and  pumps  might  be  available  to  relieve  other  parts  of 
the  city,  less  favored  in  this  respect,  it  was  necessary  to  ar- 
range that  no  more  than  a  fixed  quantity  of  sewage  should 
ever  be  relfceived  by  the  main   sewer  from   the   South  Boston 


Plate  VII. 


R^.2 


Fi^.3 


n§.4 


LARGE    REGULATOR 


PENSTOCK  GATE 

n§.6 


CONNECTION  WITH  %^  vale:  ST,  SEWER 
Fig.O  7 


SECTIONAL    PLAN 


PLAN 

BOSTON  MAIN  DRAINAGE 
INTERCEPTING  SEWERS. 

O  2  4  6  8  10 
l<d  bd  lid  M  M  M 
SCALE   OF  FEET 


BACK.  VIEW.  FRONT  VIEW 

TIDE    GATES. 


Fig.  12 


Fig.  13 


FLUSHING     GATE 

Fig.  15 


INTEECEPTIXG    SEWERS.  39 

intercepting  seTrer.  To  accomplish  this  a  "  regulator "  was 
built  into  the  intercepting  sewer  just  below  its  last  connection 
with  a  common  sewer,  at  Kemp  Street. 

A  sectional  plan  and  elevation  of  this  machine,  and  of  the 
chamber  containing  it,  is  given  by  Fig.  9,  Plate  VII. 
As  will  be  seen,  the  apparatus  is  very  simple,  and  consists  of 
stop-planks,  closing  the  sewer  from  its  top  down  to  about 
the  ordinary  dry-weather  flow  line,  the  sewer  below  the  planks 
being  lined  with  a  cast-iron  gate  frame,  or  seat,  curved  to  fit 
the  invert,  and  also  vertically  to  correspond  with  the  curve  of 
motion  of  a  cast-iron  valve,  which  plays  up  and  down  in  front 
of  it.  The  valve  is  held  by  two  cast-iron  levers,  pivoted  by  a 
3-inch  wrought-iron  shaft  in  two  bearings,  the  other  ends 
of  the  lever  being  connected  by  vertical  arms  to  a  3-inch 
square  bar.  To  the  ends  of  this  bar  are  fastened  two  boiler- 
plate floats,  placed  in  wells  on  either  side  of  the  sewer.  To 
avoid  disturbance  to  the  motion  of  the  floats,  by  waves  caused 
by  the  rush  of  sewage  under  the  valve,  water  is  brought  to  the 
wells  through  a  5-inch  pipe,  as  shoAvn,  from  a  point  50  feet 
below  the  regulator. 

The  connection  between  the  valves  and  the  floats  can  be  so 
adjusted  that  the  former  will  begin  to  close  when  the  surface  of 
sewage  in  the  sewer  has  reached  any  desired  height.  As  the 
floats  rise  the  valve  descends  until  the  opening  below  it  is  just 
sufficient  to  let  enough  sewage  pass  to  maintain  the  allowed 
depth  of  flow  in  the  sewer.  Should  the  amount  of  rain-water 
from  low  districts,  reaching  the  main  sewer  through  other 
intercepting  sewers,  exceed  the  capacity  of  the  pumps  to  con- 
trol it,  the  main  sewer  fills,  and  its  sewage  backs  up  into  the 
South  Boston  sewer,  and  still  further  raises  the  floats.  The 
opening  under  the  stop-planks  is  thus  entirely  closed,  and  all 
of  the  common  sewers  above  discharge  at  their  old  outlets,  and 
continue  to  do  so  until  the  amount  of  water  reaching  the  pumps 
can  be  controlled  by  them. 

Above  where  this  sewer  divides,  at  Hyde  Street,  the  branch 
which  turns  to  the  right,  and  skirts  the  southerly  margin  of 
South  Boston,  is  egg-shaped,  four  feet  six  inches  high  hy  three 
feet  wide  (Fig.   11,  Plate   VII.).     After   passing   under   the 


40  MAIN   DRAINAGE   WORKS. 

Old  Colony  Eailroad  the  shape  is  changed  somewhat  (Fig. 
3).  At  Vinton,  Vale,  and  other  streets,  common  sewers  are 
intercepted.  Fig.  7,  Plate  VII.,  shows  the  connection  with  the 
Vale-Street  sewer,  and  may  stand  as  a  type  of  such  connec- 
tions between  common  and  intercepting  sewers,  wherever  no 
regulation  of  the  amount  to  be  received  from  the  former  is 
required.  Nearly  every  individual  case  presented  special  con- 
ditions, which  necessitated  some  modification  of  the  method  of 
construction ;  but  the  general  plan  was  the  same  in  most  cases, 
and  its  features  are  shown  in  this  case. 

A  sump  hole,  two  feet  deep,  into  which  the  sewage  falls,  is 
first  built  in  the  common  sewer.  Into  the  bottom  of  this  sump 
is  built  a  short  section  of  iron  pipe  (Fig.  5),  from  12  to  24 
inches  in  diameter,  protected  by  a  cast-iron  flap-valve.  Ordi- 
narily this  valve  stands  open,  but  can  be  closed  if  it  is  desired 
to  break  the  connection  between  the  two  sewers.  The  bottom 
of  the  sump,  around  the  pipe,  is  rounded  ofi"  with  strong  Port- 
land cement  concrete,  so  that  there  shall  be  no  corners  in  which 
deposits  can  lodge.  The  sewage  passes  to  the  intercepting 
sewer  through  a  short  branch  connecting;  with  the  lower  end  of 
the  iron  pipe. 

Beyond  the  sump  the  common  sewer  is  provided  with  a 
chamber  containing  a  double  set  of  tide-gates.  These  gates 
give  a  clear  opening  of  from  two  to  four  feet  diameter.  Each 
set  of  gates  is  hinged  to  a  cast-iron  ring,  or  gate  seat  (Fig. 
8),  which  is  built  into  the  brick- work.  The  two  wooden  gates 
close  against  each  other.  To  make  tight  joints  the  bearing 
surfaces  of  the  gates  are  covered  with  strips  of  rubber  about 
three-eighths  of  an  inch  thick.  The  gates  are  inclined  somewhat, 
so  that  they  are  self-closing. 

From  the  main  sewer  to  the  Old  Colony  Eailroad  this  inter- 
cepting sewer  was  built  by  contract,  at  an  average  cost  of  $12.68 
per  lineal  foot.  From  the  railroad  to  H  Street  it  was  built  by 
day's  labor,  and  cost  $13.25  per  lineal  foot.  On  Ninth  Street, 
between  Old  Harbor  Street  and  G  Street,  for  a  distance  of 
about  800  feet,  the  sewer  location  crossed  a  beach  which  was 
several  feet  below  high-tide  level.  No  cofler  dam  or  other 
protection  was  used  in  this  place,  but  construction  was  carried 


INTERCEPTING    SEWERS.  41 

on  only  when  the  tide  was  down.  When  the  sea  rose  it  over- 
flowed and  filled  the  trench.  When  it  again  fell  the  water  in 
the  trench  was  let  off  through  the  sewer  already  built,  to  pumps 
at  the  pumping-station,  and  work  was  resumed.  From  H 
Street  to  N  Street,  on  Ninth  Street,  the  sewer  was  built  by 
contract.  For  about  1,000  feet,  near  K  and  L  Streets,  the 
average  depth  of  the  trench  was  about  27  feet.  The  sewer  was 
nearly  circular,  three  feet  wide  and  three  feet  two  inches  high 
(Fig.  1,  Plate  VII.).  This  section  was  among  the  earliest  built, 
and  its  design  is  not  in  accord  with  later  practice.  It  might  have 
been  made  much  more  convenient  for  workmen  to  enter,  at  slight 
additional  expense,  by  giving  it  a  greater  vertical  diameter.  Its 
fall  is  1  in  1,666|-. 

From  the  point  of  division  on  Hyde  Street  the  sewer  which 
turns  to  the  left,  and  follows  the  westerly  shore  of  South  Boston, 
is  egg-shaped,  five  feet  six  inches  by  four  feet  nine  inches,  up  to 
the  Old  Colony  Eailroad  crossing,  on  Dorchester  Avenue.  A 
timber  platform  and  rubble  masonry  side  walls  were  required  for 
the  entire  distance,  and  the  usual  cross-section  of  this  sewer  is 
shown  by  Fig.  10,  Plate  VII.  This  section  was  built  by  con- 
tract. Its  length  is  3,350  feet ;  the  average  depth  of  excavation 
was  about  24  feet,  and  the  average  cost  per  lineal  foot  was 
$16.85. 

After  taking  in  the  B-Street  sewer  the  intercepting  sewer 
changes  its  shape  (Fig.  3),  and  continues  in  Dorchester 
Avenue,  passing  under  the  N.Y.  &  N.E.  Railroad,  and  turns 
into  Foundry  Street,  which  it  follows  to  its  end,  at  the  corner 
of  Dorchester  Avenue  and  First  Street.  Considerable  difiiculty 
was  encountered  in  passing  under  the  abutments  of  the  bridge 
on  Dorchester  Avenue,  over  the  N.Y.  &  N.E.  Railroad. 
These  were  underlaid  by  running  sand,  and  the  northerly  abut- 
ment over  the  sewer,  which  had  been  built  without  mortar,  had 
to  be  taken  down.  Under  the  tracks  of  the  same  railroad, 
head-room  being  limited,  the  shape  of  the  sewer  was  altered 
(Fig.  2),  so  that  there  should  be  no  danger  of  its  interfering 
with,  or  being  injured  by,  repairs  to  the  road-bed.  This  section 
of  sewer  is  2,820  feet  long,  and  its  average  cost  per  foot  was 
$19.25. 


42  MAIN    DRAINAGE    WORKS. 

The  second  large  intercepting  sewer  which  enters  the  main 
sewer,  had  its  point  of  connection  at  the  intersection  of  East 
Chester  Park  and  Albany  Street.  It  is  called  the  East  Side 
intercepting  sewer,  and  is  located  in  streets  following  the  east- 
erly margin  of  the  city  proper  for  a  distance  of  about  21  miles. 
In  Albany  Street,  from  East  Chester  Park  to  Dover  Street,  a  dis- 
tance of  4,524  feet,  the  sewer  is  nearly  circular,  with  a  vertical 
diameter  of  five  feet  eight  inches,  and  a  horizontal  one  of  five 
feet  six  inches.  The  inclination  is  1  in  2,000.  The  average 
depth  of  excavation  for  this  section  of  work  was  24  feet,  and,  as 
marsh  mud  and  peat  extended  from  near  the  surface  of  the 
ground  to  a  depth  always  considerably  below  the  bottom  of  the^ 
sewer,  piles  were  required  to.  furnish  a  secure  foundation.  A 
timber  platform  was  fastened  to  the  tops  of  the  piles,  and  on 
the  platform  the  sewer,  with  its  rubble  masonry  abutment  walls, 
was  built.  The  bottom  of  the  excavation  was  about  6.5  feet  below 
the  elevation  of  low  tide,  and  considerable  trouble  was  experi- 
enced from  sea-water  making  its  way  into  the  trench,  esjoecially 
in  places  where  old  sea-walls  and  other  such  obstructions  were 
encountered.  The  mud  on  the  sides  of  the  trench  exerted  much 
lateral  pressure,  and  close  sheet-piling  and  heav}'^  bracing  were 
necessary.  Opening  so  deep  a  trench  in  such  material  drained 
the  water  out  of  the  adjacent  soil,  rendering  it  spongy  and  some- 
what compressible,  so  that  the  whole  street  settled  and  had  to 
be  resurfaced  and  repaved.  This  section  was  built  by  contract. 
One  firm  of  contractors  gave  up  the  job,  and  the  work  was  re-let 
under  provisions  of  the  contract.  The  average  cost  per  lineal 
foot  of  the  completed  sewer  was  $26.16. 

The  first  common  sewer  taken  in  by  the  intercepter  is  that 
on  Concord  Street.  This  sewer  drains  a  district  in  which  the 
cellars  are  not  subject  to  flooding  from  rain-water  during  high 
tides.  It  was  not  necessary,  therefore,  to  let  this  sewer  dis- 
charge into  the  intercepter  an  amount  of  sewage  in  excess  of 
its  ordinary  maximum  dry-weather  flow,  and  temporarily,  during 
rain-storms,  the  whole  dilute  contents  of  the  sewer  could,  with- 
out injury,  be  permitted  to  discharge  into  the  bay  at  the  old 
outlet.  An  arrangement  to  effect  this  was  desirable,  because, 
during  very  heavy  rain-storms,  the  whole  capacity  of  the  inter- 


INTERCEPTING    SEWERS.  43 

cepting  sewer  might  be  needed  to  aftbrd  relief  to  sewers  drain- 
ing low  districts  beyond  Concord  Street. 

Accordingly  the  connection  between  this  sewer  and  the 
intercepting  sewer  was  made  through  a  chamlier  containing  a 
small  regulating  apparatus,  designed  to  control  or  cut  oft'  the 
flow  automatically.  Figs.  1  and  2,  Plate  VIII.,  show  sec- 
tions of  this  apparatus  and  its  arrangement.  Eight  similar 
appliances,  with  slight  modifications  in  the  methods  of  arrange- 
ment, were  used  in  connection  with  the  same  number  of  common 
servers. 

The  operation  of  the  apparatus  will  be  understood  from  an 
examination  of  the  figures.  Under  ordinary  circumstances  the 
sewage  falls  into  a  sump,  and  thence  passes  to  the  regulating 
chamber,  which  it  enters  through  a  cast-iron  nozzle.  This  nozzle 
is  circular,  12  inches  in  diameter  at  its  upper  end,  and  rec- 
tangular 20  X  6  inches  at  its  orifice.  In  front  of  the  orifice 
plays  a  cast-iron  valve,  moved  by  afloat  in  a  tank  set  in  the  floor 
of  the  chamber.  The  water  in  the  tank  stands  at  the  same 
elevation  as  that  in  the  intercepting  sewer,  a  4-inch  iron  pipe 
connecting  one  with  the  other.  The  apparatus  can  be  adjusted 
so  that  the  valve  will  begin  to  close  and  cut  off*  the  flow  of 
sewage  when  the  water  in  the  intercepting  sewer  reaches  any 
desired  dei)th.  When  not  cut  off",  the  sewage  flows  around  the 
tank  and  passes  on  through  an  opening  at  its  further  end. 

The  second  common  sewer  taken  in  is  that  in  Dedham  Street. 
This  sewer  drains  a  district  which  used  to  sufifer  greatly  from 
flooding  during  rain-storms.  In  order  to  afibrd  relief  this  sewer 
was  connected  directly  with  the  intercepter  by  a  branch  two  feet 
in  diameter,  the  inlet  to  which  is  never  closed. 

The  third  sewer  taken  in  is  that  in  Union  Park  Street.  The 
district  drained  by  it  has  suflered  but  slightly  from  wet  cellars, 
and  that  only  during  severe  storms  and  very  high  tides.  The 
flow  from  this  sewer  was  regulated  in  the  same  manner  as  that 
from  the  Concord-Street  sewer,  but  the  apparatus  was  so 
adjusted  that  it  cuts  oft'  the  flow  later  than  in  the  case  of  most 
other  sewers,  and  only  when  the  intercepting  sewer  is  nearly 
full. 

'J'he  fourth  common  sewer  met  with  is  that  in  Dover  Street. 


44  MAIN    DRAINAGE    WORKS. 

This  drains  a  low  district,  and  a  free  connection,  two  feet  in 
diameter,  was  made  with  it.     According  to  the  usual  practice 
in  such  cases  this  sewer  would  have  been  connected  with  tlie 
intercepter  at  or  near  the  point  in  Albany  Street  where  their 
two  locations  intersect.     But  it  was  found    in    examining  the 
city  sewers,  with  reference  to  connections  with  them,  that  the 
Dover-Street  sewer  was  not  in  condition  to  be  intercepted  at 
any  point  east  of  Harrison  Avenue.     Between  that  street  and 
its  outlet  it  is  a  rectangular  wooden  structure,  5  x  ^  feet  in 
dimensions,  placed   close  to  an  old  stone    retaining-wall   and 
surrounded  b}^  loose  stone  ballast.     It  is  considerably  broken, 
so  that  the  tide-water  from  the  bay  which  ebbs  and  flows  about 
the  wall  and  in  the  ballast  has  free  access  to  the  sewer,  and 
would    have    flowed    into    the    intercepting    sewer,    and    so 
reached   the   pumps.     From   Harrison   Avenue    westerly,  the 
Dover-Street  sewer  was  built  of  brick,  and  was  tight  so  that  sea- 
water  could  be  excluded  from  it  by  tide-gates.     Accordingly 
the  connection  was  made  west  of  Harrison  Avenue,  and  a  2  X  3 
feet  oval  branch  sewer  (Fig.  3),  588  feet  long,  was  built  from 
that  point  to  convey  the  sewage  to  the  intercepting  sewer  at 
Albany  Street. 

Above  Dover  Street  are  few  districts  which  sufi'er  from  flood- 
ing. Accordingly  a  large  regulating  apparatus,  to  control  the 
flow  from  above,  was  built  into  the  intercepting  sev/er  at  this 
point.  It  resembled  that  on  the  South  Boston  sewer,  before 
described,  and  shown  on  Plate  VII,  by  Fig.  9. 

From  Dover  Street  to  its  upper  end  on  Atlantic  Avenue  the 
East  Side  sewer  was  built  by  day's  labor,  under  a  superintend- 
ent appointed  by  the  city.  This  was  done  because  above 
Dover  Street  the  sewer  location  was  confined  to  crowded 
thoroughftires,  in  which  peculiar  management  was  required  to 
prevent  serious  obstruction  to  travel  and  to  the  business  of 
abutters ;  and  also  because,  operations  being  principally  car- 
ried on  in  filled  land,  beds  of  dock  mud,  old  walls,  wharves, 
and  other  obstructions  were  continually  encountered,  requiring 
frequent  changes  in  methods  of  construction  which  could  not  be 
foreseen  and  provided  for  in  the  specifications  of  a  contract. 

From  Dover   Street  the  sewer  location  extends    in  Albany 


-Plate   Vlir, 


1- 

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, 

iNTERGEPJlNCi 

-s- 

\ 

Ay 

\/ 

/ 

/W 

// 

REGULA" 

o 

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/ 

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SUMP 

GENERAL  PLAN    OF 
CONCORD   ST.  CONNECTION 


Fig.  14  Fig.  15 

BOSTON    MAIN   DRAINAGE, 

INTERCEPTING    SEWERS. 


10  15  20  FEET 


O  5  10  15  20 

hH-ri-H4n.4--i--h-ht-i--Lr-M^ 


SECTIONAL     PLAN. 


FALMOUTH    ST.  SEWER. 


>  INTERCEPTING    SEWERS.  45 

Street  to  Lehigh  Street,  at  which  point  it  enters  private  land,  and 
crosses  the  freight  and  switch  yards  of  the  Boston  and  Albany, 
and  Old  Colony  Railroads,  to  Federal  Street  near  the  bridge, 
a  total  distance  of  2,331.5  feet.  In  Albany  and  Lehigh  Streets 
are  the  tracks  of  a  Freight  Railway  Company,  and  in  the  rail- 
road yards  are  about  40  lines  of  rails  in  constant  use,  which 
it  was  very  important  should  not  be  disturbed.  The  whole 
section  of  work  is  in  tilled  land,  underlaid  by  beds  of  mud  from 
5  to  20  feet  deep,  below  the  bottom  of  the  sewer,  which  is 
itself  several  feet  below  the  level  of  low  tide.  At  different 
points  obstruction  in  the  shape  of  old  walls  and  wharves  were 
encountered,  which  admitted  sea-water  freely  to  the  trench,  so 
that,  as  a  rule,  work  could  only  progress  during  low  stages  of 
the  tide. 

The  sewer  is  oval,  five  feet  high  (Fig.  4),  and  generally 
required  piling  for  its  support.  It  is  built  partly  of  wood,  lined 
with  two  inches  of  concrete,  and  partly  of  brick-work  resting  on 
a  solid  cradle  of  wood,  six  inches  thick.  Travel  upon  the  streets 
was  not  interrupted,  and  with  considerable  difiiculty  the  freight- 
railway  tracks  were  supported  and  maintained.  As  it  would 
have  been  impossible  to  have  had  an  open  trench  through  the 
Albany  and  Old  Colony  Railroad  yards  without  interfering  with 
their  traflac,  operations  at  that  point  were  carried  on  entirely 
below  the  surface.  The  tracks  were  supported  by  stringers, 
and  the  spaces  between  them  floored  over.  By  the  use  of 
special  machinery  all  the  earth  excavated  or  refilled,  as  well  as 
materials  for  constructions,  was  conveyed  by  tracks  suspended 
below  the  floor.  The  trench  was  well  braced,  and  its  sides  pro- 
tected by  lag-sheeting,  which,  together  with  the  piles  driven  to 
support  the  sewer,  were  all  put  in  place  without  encroaching 
upon  the  surface.  It  is  believed  that  not  a  single  train  was 
delayed,  nor  any  inconvenience  caused,  by  these  operations. 
The  average  cost  of  this  section  of  sewer  was  about  $31.26  per 
lineal  foot. 

In  Federal  Street,  and  Atlantic  Avenue  to  its  end  at  Central 
Street,  the  intercepting  sewer  is  oval,  four  feet  six  inches  high  by 
two  feet  eight  inches  wide.  Fig.  5,  Plate  VIII. ,  shows  the  usual 
mode  of  construction.     Federal  Street  contained  double  horse- 


46  MAIN    DRAINAGE    WOEKS. 

railroad  and  single  freight-raihvay  tracks,  and  beneath  its  sur- 
face were  one  sewer,  two  water  pipes  and  two  gas  pipes. 
Beds  of  dock  mud  extended  from  5  to  20  feet  below  the  bottom 
of  the  new  sewer,  and  old  dock  walls  and  timber  structures 
were  frequently  encountered.  A  location  on  the  east  side  of 
the  street  was  found  to  be  most  practicable,  and  the  sewer  was 
built  by  methods  which  left  the  roadway  open  for  travel.  By 
flooring  over  the  trench  at  intervals,  passages  were  maiutained 
through  the  excavating  machine  (shown  on  Plate  XXV.)  to  the 
yards  and  wharves  bordering  Fort  Point  Channel. 

The  freight-railway  tracks  were  shifted  towards  the  centre 
of  the  street,  and  were  used  during  the  day  for  the  passage  of 
horse-cars  in  one  direction.  Bricks,  cement,  and  other  mate- 
rial were  piled  on  the  outer  edges  of  both  sidewalks  where 
they  would  cause  least  inconvenience,  and  always  so  as  to  leave 
a  clear  passage-way  four  feet  wide.  Endeavors  were  made  to 
cause  the  least  possible  annoyance  to  corporations  and  individu- 
als ;  and  in  general  these  efl:brts  seemed  to  be  appreciated  and 
reciprocated  by  the  public,  so  that  complaints  were  rare. 
This  section  of  work  was  5,159  feet  long.  The  average  depth 
of  excavation  was  about  21  feet,  and  the  average  cost  of  com- 
pleted sewer  was  $15.06  per  lineal  foot.  The  Stony-Brook  in- 
tercepting sewer  joins  the  main  sewer  at  the  intersection  of 
Camden  and  Tremont  Streets.  This  sewer  intercepts  the  sew- 
age which  formerly  emptied  at  seven  outlets,  into  Stony  Brook, 
and  thence  found  its  way  into  the  Back  Bay.  In  Tremont  and 
Cabot  Streets,  from  Camden  to  Euggles  Street  (Plate  V.),  a 
distance  of  2,135  feet,  the  sewer  was  built  by  contract.  The 
rate  of  inclination  is  1  in  700,  and  the  average  depth  of  excava- 
tion required  was  21  feet.  The  sewer  is  nearly  circular,  four  feet 
six  inches  wide  by  four  feet  eight  inches  high,  and  is  chiefly 
founded  on  clay,  so  that  side  walls  were  only  needed  for  about 
300  feet,  and  the  average  cost  per  lineal  foot,  including  inspec- 
tion, was  $11.97.  The  customary  iron  penstock  gate  w^as  built 
into  the  sewer  just  above  the  bell-mouth  connection  chamber 
by  which  it  joins  the  main. 

As    the    territory  drained  by  the  sewers  which  empty  into 
Stony  Brook  is  high  land,  a  large  automatic  regulating  appara- 


INTERCEPTING   SEWERS.  47 

tus,  similar  to  the  one  shown  on  Phite  VII.,  was  ])uilt  into  the 
intercepting  sewer  at  Rnggles  Street,  by  means  of  which  the 
flow  is  partly  or  wholly  cut  off  during  severe  and  continuous 
rain-storms.  Above  the  regulator  is  a  three-way  bell-mouth 
chamber  (Fig.  10,  Plate  VIII.),  from  which  radiate  three 
principal  branch  sewers.  The  centre  or  main  branch,  al)out  4^ 
feet  in  diameter,  is  1,700  feet  long,  and  intercepts  the  sewage 
formerly  discharging  into  the  brook  by  outlets  at  Elmwood  and 
Hampshire  Streets.  This  sewer  passes  twice  under  the  brook, 
at  so  low  an  elevation  that  it  preserves  its  regular  grade  and 
shape.  The  other  two  branches  are  Ijuilt  just  large  enough  to 
enter,  being  2x3  feet,  egg-shaped,  with  the  smaller  end 
down.  These  also  cross  twice  under  the  brook,  at  Tremont 
Street  and  at  Ruggles  Street.  Including  the  regulating  cham- 
ber, and  all  sewers  above  it,  this  section  of  work  was  built  by 
the  day,  under  the  City  Superintendent,  Mr.  H.  A.  Carson. 
There  were  built  in  all  4,229  lineal  feet  of  sewers,  includin£>-415 
feet  of  15-inch  pipe.  The  average  cost  per  foot  of  the  whole 
was  $14.30.  A  considerable  portion  of  the  2X3  feet  sewers 
was  built  during  the  winter  of  1880-81.  The  sewers  were 
from  14  to  19  feet  below  the  street  surface,  and  the  excavation 
was  done  by  tunnelling  from  pits  about  10  feet  apart.  The 
outlets  of  the  city  sewers  being  below  the  level  of  high  tide,  in 
order  to  prevent  back-water  reaching  the  intercepting  sewer,  it 
was  necessary  to  build  gate-chambers  just  beyond  the  points 
of  interception,  each  chamber  containing  a  double  set  of  tide- 
gates. 

The  last  of  the  large  intercepting  sewers  joins  the  main  sewer 
at  its  present  end  at  the  intersection  of  Camden  Street  with 
Huntington  Avenue  (Plate  V.).  It  is  commonly  called  the 
West  Side  intercepting  sewer,  and  is  located  in  streets  border- 
ing the  westerly  margin  of  the  city  proper,  and  intercepts  the 
sewage  which  formerly  discharged  into  Charles  River.  This 
sewer  is  about  3|  miles  long,  and  its  inclination  from  end  to  end 
is  1  in  2,000. 

From  the  main  sewer  to  Beacon  Street,  and  in  that  street  to 
Charles  Street,  a  distance  of  9,325  feet,  the  West  Side  sewer 
was  built  by  day's  labor,  at  an  average  cost  of  $13.35  per  lineal 


48  MAIN   DRAINAGE    WORKS. 

foot.  This  section  of  work  includes,  besides  the  customary 
man-holes,  six  common-sewer  connections,  five  small  regulators, 
one  side  entrance,  one  penstock,  and  three  flushing-gates.  The 
usual  form  of  this  sewer  is  shown  by  Fig.  8,  Plate  VIII.  It  is 
egg-shaped,  five  feet  six  inches  high  by  four  feet  nine  inches  wide. 
It  will  be  noticed  that  the  usual  position  given  to  an  egg-shaped 
sewer  is  reversed  in  this  case,  the  larg-er  end  of  the  ess:  formino- 
the  invert.  This  position  was  adopted  because,  while  affording 
convenient  head-room,  it  kept  the  flow  line  as  low  down  as  was 
practicable.  As  the  flow  in  this  sewer  is  always  a  foot  or 
more  deep,. the  hydraulic  mean  depth,  and  consequently  the 
velocity  of  flow,  is  greater  than  it  would  have  been  had  the 
smaller  end  of  the  sewer  been  below. 

A  case  of  slight  injury  to  this  sewer  may  be  worth  noticing. 
When  the  sewer  was  built  on  the  line  of  Falmouth  Street  that 
street  had  not  yet  been  filled  and  graded,  and  the  mud  and  peat, 
which  underlay  the  marsh  surface  in  that  locality,  sometimes  ex- 
tended down  below  the  top  of  the  sewer.  About  a  year  after- 
wards the  street  was  graded  with  gravel  about  seven  feet  high 
above  the  original  surface  of  the  marsh  over  the  sewer.  One 
side  of  the  street  was  filled  before  the  other,  and  the  unequal 
pressure  which  resulted  was  transmitted  to  the  sewer,  and 
caused  its  arch  to  bulge,  as  shown  by  Fig.  12.  Fortunately  the 
amount  of  distortion  was  not  sufficient  to  endanger  the  sewer's 
stability,  and  the  crack  was  pointed  with  Portland  cement. 

In  Hereford  Street,  for  a  distance  of  282  feet,  the  sewer  lo- 
cation passed  under  a  freight-yard  of  the  Boston  &  Albany 
Railroad,  in  which  were  about  20  lines  of  track.  Piles  were 
driven  and  stringers  placed  to  support  these  tracks,  and  nearly 
all  of  the  sewer  building  operations  were  carried  on  beneath 
the  surface  of  the  ground,  so  that  the  traffic  of  the  railroad  was 
not  interfered  with.  At  this  point,  and  beyond  the  railroad 
location  for  a  total  length  of  about  800  feet  in  Hereford  Street, 
a  common  sewer  was  built  in  the  same  trench,  directly  above 
the  intercepting  sewer.  This  was  done  by  an  arrangement  with 
the  City  Sewer  Department,  which  designed  and  paid  for  the 
upper  sewer.  A  cross-section  of  the  two  sewers,  showing  their 
arrangement,  is  shown  by  Fig.  9. 


INTERCEPTING    SEWERS.  49 

In  Beacon  Street,  for  a  distance  of  590  feet  in  the  vicinity  of 
Exeter  Street,  22  old  stone  walls,  from  five  to  twelve  feet  thick, 
were  encountered  and  had  to  ])e  cut  through.  These  walls  con- 
stituted the  sluiceway  of  the  old  mill-dam,  and  their  removal 
caused  considerable  delay.  The  cost  of  excavation  per  lineal 
foot  of  trench,  20  feet  deep  in  this  street,  varied  from  $3.94  to 
$14.49.  The  section  from  Camden  to  Charles  Street  was 
built  in  1878.  During  a  portion  of  the  season  work  was  car- 
ried on  day  and  night  at  two  different  points.  The  largest 
number  of  men  and  boys  employed  at  any  one  time  was  369. 
The  rate  of  progress  varied  greatly  ;  where  no  special  obstacles 
were  met,  108  feet  of  completed  sewer  was  built  each  24 
hours. 

On  Beacon  Street  the  large  common  sewers  in  Hereford, 
Fairfield,  Dartmouth,  and  Berkeley  Streets  are  intercepted. 
The  sewage  from  each  of  these  sewers  passes  to  the  intercept- 
ing sewer  through  a  chamber  in  which  is  a  small  automatic 
regulating  apparatus,  similar  to  the  one  shown  on  Plate  VIII., 
so  adjusted  as  to  cut  off  the  flow  whenever  the  water  in  the 
intercepting  sewer  exceeds  an  established  depth.  The  sewers 
just  mentioned  are  too  low  to  pass  over  the  intercepting  sewer, 
and  a  somewhat  different  method  of  construction  was  necessary 
in  connecting  them.  The  arrangement  at  Berkeley  Street  is 
shown  by  Fig.  13,  Plate  VIII. 

A  secondary  intercepting  sewer  was  built  in  Brimmer  Street, 
which  collects  all  of  the  sewage  flowing  westward  from  Beacon 
Hill,  and  conveys  it  to  the  principal  intercepting  sewer  in  Bea- 
con Street.  For  the  sake  of  economy  and  simplicity,  the  old 
outlets  of  the  common  sewers  in  Eevere,  Pinckney,  Mt.  Ver- 
non, Chestnut,  and  Beacon  Streets  were  abandoned,  and  the 
total  flow  from  these  sewers,  including  rain,  is  taken  by  the  new 
Brimmer-Street  sewer,  a  single  storm  overflow  being  provided 
at  Back  Street.  The  construction  of  the  Brimmer-Street  sys- 
tem involved  the  building  of  1,456.5  feet  of  oval  brick  sewers, 
varying  from  2X3  feet  to  3  X  4  feet  6  inches  in  diameter ; 
also  the  rebuilding  of  about  556  feet  of  common  sewers,  which 
were  found  to  be  too  low  or  otherwise  defective.  The  flow 
from  the  Brimmer-Street  sewer  into  the  intercepting  sewer  in 


50  MAIN   DRAINAGE    WORKS. 

Beacon  Street  is  regulated  in  the  same  manner  as  that  from  the 
ordinary  city  sewers. 

A  little  beyond  Brimmer  Street  a  large  common  sewer,  which 
comes  from  the  south  across  the  Public  Garden,  is  intercepted. 
This  drains  what  is  called  the  Church-Street  district,  compris- 
ing low  territory,  in  which  are  many  cellars  which  used  often 
to  be  inundated.  Sewage  from  this  sewer,  therefore,  is  taken 
directly  into  the  intercepting  sewer  without  the  intervention 
of  any  regulating  apparatus. 

On  Charles  Street,  from  Beacon  to  Cambridge  Street,  a  dis- 
tance of  1,832  feet,  the  sewer  was  built  by  contract.  It  is  Qgg- 
sliaped,  4  X  4.5  feet  in  diameter  (Figs.  6  and  7),  and  cost 
$10.10  per  lineal  foot.  This  was  the  only  section  of  the  West 
Side  sewer  which  was  built  by  contract.  In  excavating  the 
trench  many  of  the  hollow-log  water-pipes  of  the  old  Jamaica 
Pond  Aqueduct  Company  were  found  in  a  perfect  state  of  pres- 
ervation. A  house-drain  was  found  which  the  drain-layer  had 
connected  with  one  of  these  water-pipes,  although  the  street 
sewer  was  but  a  few  feet  distant.  The  log  had  but  three  inches' 
bore,  and,  of  course,  led  to  no  outlet. 

At  the  intersection  of  Cambridge  and  Charles  Streets  a  large 
automatic  regulating  apparatus,  similar  to  the  one  shown  on 
Plate  VIL,  was  built  into  the  sewer,  to  control  the  flow  from 
above.  The  excavation  in  which  the  chamber  for  this  appa- 
ratus was  built  was  30  feet  square ;  but,  by  flooring  over  the 
top  of  the  excavation,  and  supporting  the  various  lines  of  street- 
railway  tracks  at  that  place,  travel  was  not  impeded,  all  build- 
ing operations  being  carried  on  below  the  surface  of  the  street. 

From  Cambridge  to  Leverett  Street,  a  distance  of  2,150  feet, 
the  intercepting  sewer  is  oval,  four  feet  six  inches  by  three  feet 
in  diameter.  It  is  of  brick-work,  eight  inches  thick,  and  usu- 
ally required  a  timber  cradle  support.  The  work  on  this  section 
presented  the  usual  difficulties  met  with  in  excavating  through 
filled  land,  in  the  way  of  old  obstructions  and  the  free  access  of 
tide-water.  By  a  rather  curious  coincidence,  for  a  distance  of 
about  500  feet,  the  remains  of  an  old  wharf  or  bulkhead  were 
found,  with  longitudinal  rows  of  piles  within  the  trench  in  such 
positions  that,  by  cutting  them  ofl'at  the  proper  elevation,  they 


INTERCEPTING   SEWERS.  51 

served  as  a  support  for  the  sewer,  in  the  place  of  new  piles  which 
would  otherwise  have  been  necessary.  Seven  hundred  and  one 
feet,  in  all  of  the  Fruit-Street  and  Livingstone-Street  sewers, 
which  were  too  low  to  be  intercepted,  were  replaced  by  2  X  3 
feet  oval  brick  sewers.  The  private  sewer  from  the  Massachusetts 
General  Hospital  was  also  too  low  to  be  intercepted.  This  was 
found  to  be  a  rectangular  wooden  scow,  2.5  X  2.5  feet  in  diam- 
eter, Avith  its  bottom  at  low-tide  level.  The  Trustees  of  the 
hospital  themselves  replaced  it  with  a  10-inch  drain-pipe  at  a 
higher  elevation. 

From  Charles  Street  to  its  upper  end  at  Prince  Street,  a  dis- 
tance of  3,571  feet,  the  West  Side  sewer  maintained,  Avith  rare 
exceptions,  an  even  size,  of  three  feet  wide  and  four  feet  six 
inches  high.  The  arch  consisted  of  eight  inches  of  brick,  and 
the  invert  was  generally  made  with  four  inches  of  brick  resting 
on  a  timber  cradle,  also  four  inches  thick.  The  common  sewer 
in  Lowell  Street,  which  was  a  large,  flat-bottomed  wooden  scow, 
was  too  low  to  be  intercepted.  It  was  accordingly  abandoned, 
and  all  branch  sewers  and  house-drains  were  connected  directly 
with  the  intercepting  sewer.  To  facilitate  making  these  connec- 
tions the  intercepting  sewer  w^as  located  exactly  on  the  line  of 
the  old  sewer.  The  top  planks  of  the  latter  were  removed,  but 
its  side  planks  were  retained,  and  the  new  sewer,  with  its  width 
reduced  to  two  feet  eight  inches,  was  built  between  them.  The 
flow  of  sew'ase  was  maintained  durino-  construction  throuoh 
channels  above  the  floor  of  the  old  sewer  and  below  the  bottom 
of  the  new  one,  which  was  supported  on  timber  saddles  (Fig. 
14,  Plate  VIII.). 

Causeway  Street  is  one  of  the  most  crowded  thoroughfares  of 
the  city.  It  contains  two  lines  of  track  for  horse-cars  and  one 
for  freight-cars.  On  its  north-westerly  side  are  the  depots  of 
three  railroads,  with  no  outlet  for  their  passengers  and  freight 
except  into  this  street.  The  tracks  of  another  railroad  cross 
the  street.  The  territory  traversed  by  the  street  is  all  made 
land,  consisting  of  loose  materials  filled  upon  a  mud  bottom. 

It  was  with  some  apprehension  of  trouble  that  work  was 
begun  on  this  section.  The  most  difficult  feature  of  the  work 
was  so  to  conduct  it  that  travel  should  not  be  seriously  impeded. 


52  MAIN   DRAINAGE   W0EK8. 

Owing  to  the  skill  and  care  of  the  superintendent  and  his  subor- 
dinates, and  to  the  appliances  used  for  handling  the  earth  and 
other  material,  the  sewer  in  this  street  was  built  within  four 
months,  without  closing  any  portion  of  the  street  to  travel,  and 
with  the  minimum  of  inconvenience  to  the  public.  At  street- 
crossings  and  entrances  to  railroad-yards,  work  was  carried  on 
below  timber  platforms,  or  bridges,  without  encroaching  upon 
the  street  surface.  In  crossing  the  Boston  and  Maine  Railroad 
tracks,  the  excavating  apparatus,  with  its  steam-engine,  was  so 
elevated  as  to  leave  head-room  for  the  passage  of  trains. 
Plate  IX.  is  from  a  photograph  taken  at  this  point. 

As  a  precaution,  where  the  foundation  seemed  insecure,  the 
vertical  diameter  of  the  sewer  was  increased  by  six  inches,  so 
that,  should  slight  unequal  settlements  occur,  the  invert  may  be 
brought  to  its  true  grade  without  lessening  the  desired  size  of 
the  sewer.  For  about  76  feet,  to  avoid  interfering  with  the 
street  surface,  the  intercepting  sewer  was  built  entirely  within 
an  abandoned  common  sewer  (Fig.  15,  Plate  VIII.).  At  the 
upper  end  of  the  intercepting  sewer,  at  Prince  street,  the  grade 
of  the  invert  is  about  four  feet  above  mean  low  water,  which  is 
the  highest  elevation  of  any  portion  of  the  Main  Drainage  Sys- 
tem. At  this  point  a  direct  connection  with  the  harbor  has 
been  made,  which  is  closed  under  ordinary  circumstances  by  a 
three  feet  square  penstock  gate.  By  opening  this  gate  at  the 
time  of  high  tide  the  sewer  can  be  thoroughly  flushed. 


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CHAPTER  VII. 

PUMPING-STATION. 

As  before  stated,  and  as  shown  by  the  plan  (Plate  V.),  the 
Main  Drainage  Pumping-Station  is  situated  at  Old  Harbor 
Point,  on  the  sea-coast  in  Dorchester,  about  a  mile  from  any 
dwelling.  In  flowing  by  gravitation  to  this  point  the  sewage 
has  descended,  so  that  it  is  from  11  to  14  feet  below  the  eleva- 
tion of  low  tide.  To  reach  its  final  destination  it  must  flow 
about  21  miles  further,  to  Moon  Island,  and  be  high  enough, 
after  arrivino-  at  the  storao-e  reservoir  on  the  Island,  to  be  let 
out  into  the  harbor  at  the  time  of  high  water.  That  it  may  do 
this  it  must  first  be  raised  by  an  average  lift  of  35  feet. 

The  essential  parts  of  the  pumping-station  are :  a  filth- 
hoist  (so  called),  where  the  sewage  passes  through  screens  to 
remove  solid  matters  which  might  clog  the  pumps  ;  pump-wells, 
into  one  or  more  of  which  the  sewage  can  be  turned ;  pumping- 
engines  to  raise  the  sewage  ;  an  engine-house  to  protect  the 
engines ;  a  boiler-house,  containino;  boilers  to  furnish  steam 
power ;  a  coal-house  to  store  a  supply  of  coal,  and  a  dock  and 
wharf,  where  vessels  bringing  coal  can  be  unloaded.  The  posi- 
tion and  arrangement  of  these  principal  structures  and  apparatus 
are  shown  on  Plate  X. 

The  filth-hoist  is  a  solid  masonry  structure,  extending  from 
the  surface  of  the  ground  down  to  below  the  main  sewer.  Its 
inside  dimensions  are  25  X  32  feet,  and  its  exterior  walls  are  from 
4  to  5  feet  thick,  founded  upon  two  courses  of  10-inch  timber. 
In  excavating  for  building  the  filth-hoist,  the  ground,  which  con- 
sisted of  wet  sand,  was  held  by  round  wooden  curbs.  The 
total  depth  of  excavation  was  35  feet,  and  the  upper  12  feet 
were  dug  without  bracing  to  natural  slopes.  Below  this,  three 
tiers  of  4-inch  sheet  planks,  each  10  feet  long,  were  driven,  and 
were  braced  by  circular  ribs.  The  three  curbs  were  71.61 
and  57  feet  in  diameter,  respectively,  and  by  this  method  of 


54  MAIN   DRAINAGE   WORKS. 

bracing  an  unobstructed  space  was  secured  for  building  the 
masonry. 

As  will  be  seen  by  referring  to  Plates  X.  and  XI.,  the  main 
sewer  passes  through  the  westerly  foundation  wall  of  the  filth- 
hoist.  At  this  point  the  sewer  has  granite  voussoirs  cut  to 
form  a  bell  shaped  opening.  Facing  the  sewer  opening  are  two 
gate-openings,  protected  by  iron  penstock  gates,  7  X  6.5  feet 
each,  throuo^h  one  or  both  of  which  the  sewas^e  flows.  These 
gates  are  counterbalanced  and  are  moved  by  hydraulic  pressure 
derived  from  a  city  water-pipe.  The  pressure  is  sufficient  to 
move  them  freely  ;  but  to  start  them  when  down,  with  a  head  of 
water  against  them,  a  hydraulic  force  pump  is  added,  by  means 
of  which  the  initial  pressure  can  be  increased  to  any  extent  re- 
quired. Beyond  the  gates  the  structure  is  divided  longitudinally 
by  a  brick  partition  wall  into  two  parts,  in  each  of  which  are 
chambers  containing  two  independent  cages,  or  screens,  one 
before  the  other.  The  cages  are  rectangular  in  shape  7  feet  8 
inches  high,  7  feet  3|-  inches  wide,  and  3  feet  4^  inches  deep. 
They  are  shown  in  detail  by  Fig.  4  on  Plate  XIV.  Their 
backs,  sides,  and  tops  are  formed  of  |-inch  round  iron  rods, 
with  1-inch  spaces  between  them.  The  cages  are  counterbal- 
anced, and  are  raised  and  lowered  by  four  small  steam-engines. 
The  steam  for  these  engines,  as  well  as  for  heating  purposes, 
is  brought  underground  from  the  boiler  house.  The  super- 
structure of  the  filth-hoist  is  30  X  37  feet  outside  dimensions, 
and  is  built  of  quarry-faced  granite  dimension-stones,  lined 
inside  with  brick.  A  view  of  the  outside  of  this  building  is 
shown  at  the  left  side  of  Plate  XVII.  Plate  XIL  is  from  a 
photograph  taken  inside  of  the  filth-hoist  when  one  pair  of 
cages  was  raised.  It  gives  a  general  idea  of  the  arrangement 
of  the  hoisting  machinery. 

After  passing  through  the  cages  the  sewage  is  conveyed  by 
one  or  both  of  two  sewers,  nine  feet  in  diameter  each,  to  galleries 
on  either  side  of  the  engine-house  substructure,  from  which 
galleries  it  can  be  admitted  through  gate  openings  to  one  or 
more  pump-wells,  situated  between  the  galleries.  The  bottom 
of  the  pump-wells  is  19.5  feet  below  low-tide  level  and  36.5 


MAIN  SEWER 


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PUMPING-8TATI0N.  55 

feet  below  the  surface  of  the  ground.  From  the  wells  the  sew- 
age is  raised  by  the  pumps  to  its  required  elevation. 

The  complete  design  of  the  pumping-station,  as  indicated  on 
Plate  X.,  consists  of  an  engine-house,  two  boiler-houses  and  a 
coal-house,  so  arranged  as  to  include  a  court-yard.  The  build- 
ings are  to  be  of  dimensions  suitable  for  containing  eight  pump- 
ina-enirines  with  their  boilers  and  other  appurtenances.  Only 
the  portions  of  these  buildings  shown  on  the  plan  by  full  lines 
are  at  present  constructed  or  needed. 

The  foundation  walls  of  the  engine-house  aggregate  about 
350  feet  in  length.  They  are  37.5  feet  in  height  and  nine  feet 
thick  at  the  bottom,  where  they  rest  on  a  timber  platform,  24 
inches  thick,  which  also  extends  under  the  whole  building,  and 
furnishes  a  foundation  course  for  the  piers  which  support  the 
engines.  To  build  the  exterior  walls  trenches  16  feet  wide 
were  first  excavated.  A  core  of  earth  was  left  inside  these 
trenches  until  the  walls  had  been  erected,  when  it  was  removed 
to  make  place  for  the  pump-wells  and  engine  foundations.  The 
exterior  retainins^  and  foundation  walls  were  built  of  granite, 
and,  although  called  rubble  masonry,  yet,  owing  to  the  sizes 
and  shapes  of  stones  used  and  the  care  taken  in  selecting  and 
laying  them,  the  work  more  nearly  resembles  a  fair  quality  of 
roughly  coursed  block-stone  work. 

The  pump-wells  and  engine  foundations  are  built  chiefly  of 
brick,  but  contain  in  addition  about  300  dressed  granite  stones. 
These  stones  are  used  for  copings,  as  bearings  for  holding-down 
bolts,  for  lining  gate  and  other  openings,  etc.,  etc.  There  are 
nine  iron  gates,  with  suitable  attachments  and  shafting,  operated 
hj  two  small  steam-engines.  Eight  of  these  gates,  4  feet  9^ 
inches  bj^  6  feet  3^  inches  each,  control  the  flow  of  sewage  from 
the  side  galleries  into  the  four  pump-wells.  Another  gate,  4  X 
4  feet  square,  controls  the  admission  of  salt  water  from  the  salt- 
water conduit. 

This  last-mentioned  structure,  as  shown  by  the  plan  (Plate 
X.),  is  a  solid  masonry  conduit,  with  its  bottom  six  feet  below 
the  elevation  of  low  tide,  and  connects  tide-water  at  the  dock 
with  one  of  the  engine-house  galleries.  Its  ofiice  is  to  conduct 
salt  water  to  the  engine-house  for  use  in  the  condensers,  and 


56  MAIN   DRAINAGE   WORKS. 

also  to  furnish  an  additional  supply  of  water  to  the  pumps  for 
flushing  or  other  purposes,  whenever  the  amount  of  sewage  re- 
ceived from  the  main  sewer  is  insufficient  for  such  purposes. 

As  has  been  stated,  the  sewage  is  elevated  to  heights  (de- 
pending at  any  time  upon  the  depth  of  sewage  in  the  reservoir) 
which  average  about  35  feet. 

As  the  city  sewers  receive  rain-water,  and  as  it  is  desired  to 
take  as  much  of  this  as  possible,  especially  from  certain  districts, 
it  follows  that  during  short  periods  of  time,  when  it  rains,  very 
much  greater  pumping  capacity  is  needed  than  is  usually  suffi- 
cient. There  must,  therefore,  be  a  pump,  or  pumps,  to  run 
continuously,  and  others  to  run  only  when  it  rains  or  thaws. 

The  chief  item  of  expense  in  pumping  is  the  cost  of  fuel. 
For  the  sake  of  economy  the  pumping  engines  for  continuous 
service  must  do  their  work  with  as  little  consumption  of  fuel  as 
possible,  and  to  accomplish  this  an  expensive  machine  can  be 
afibrded.  For  the  engines  which  run  onlj^  occasionally  cheaper 
machines  are  more  economical,  the  saving  in  interest  on  the  first 
cost  more  than  compensating  for  the  extra  fuel  consumed  by 
them.  The  pumping  plant  of  the  Boston  Main  Drainage  Works 
includes  two  expensive  high-duty  engines  and  two  cheaper  lower- 
duty  engines. 

The  high-duty  engines  were  designed  by  Mr.  E.  D.  Leavitt, 
Jr.,  on  general  specifications  prepared  by  the  City  Engineer, 
Mr.  Davis.  They  were  built  by  the  Quintard  Iron  Works,  of 
New  York,  and  cost  about  $115,000  each.  A  plan  and  elevation 
of  one  of  them  is  given  on  Plate  XIII. 

As  Avill  be  seen,  it  is  a  compound  beam  and  fly-wheel  engine, 
working  two  single-acting  plunger-pumps.  The  steam  cylin- 
ders are  vertical  and  inverted,  their  axes  coinciding  with  those 
of  the  pumps  below  them,  the  pistons  of  the  engines  and 
plungers  of  the  pumps  being  connected  in  the  same  line  with 
the  ends  of  the  beam. 

In  designing  these  engines  particular  attention  was  given  to 
the  following  conditions  :  — 

First.  The  distribution  of  the  weight  of  the  engine  so  as 
not  to  produce  concentrated  pressure  on  any  part  of  the  foun- 
dations. 


Plate  XII. 


PUMPING-STATION.  57 

Second.  Great  strength  in  the  details  and  combinations  of 
the  parts,  to  render  the  h'ability  of  breakage  a  minimum. 

Third.  A  proportion  of  the  wearing  surfaces  such  as  will 
allow  of  an  uninterrupted  running  for  extended  periods,  with 
the  least  wear. 

Fourth.  Easy  accessibility  of  all  the  parts  for  examination, 
repairs,  and  renewals. 

Fifth.  An  adaptation  of  the  pumps  and  their  valves  to  the 
peculiar  duty  required  of  them,  i.e.,  to  allow  the  passage  of 
rags,  sticks,  and  such  other  small  bodies  as  will  not  be  detained 
by  the  filth-hoist ;  and,  in  addition,  a  construction  which  will 
admit  of  the  easy  removal  of  an  entire  pump  or  any  of  its 
parts,  without  disturbing  any  important  part  of  an  engine. 

Sixth.  A  high  degree  of  economy  in  the  consumption  of 
coal. 

The  following  are  a  few  of  the  leading  dimensions  :  — 

Diameter  of  high-pressure  cylinder,  2b\  inches. 

Diameter  of  low-pressure  cylinder,  52  inches. 

Diameter  of  plunger,  48  inches. 

Stroke,  9  feet. 

Distance  between  centres  of  cylinders,  15  feet  2  inches. 

Eadius  of  beam  to  end  centres,  8  feet  3  inches. 

Radius  of  crank,  4  feet. 

Diameter  of  fly-wheel,  36  feet. 

Weight  of  fly-wheel,  36  tons. 

Nominal  capacity,  25,000,000  gallons  a  day. 

Speed  for  capacity,  11  strokes  per  minute. 

Steam  at  a  pressure  of  about  100  pounds  is  admitted  from 
the  supply-pipe,  A  (see  Plate  XIII.),  through  the  side-pipe,  B, 
to  the  steam-chests  of  the  high-pressure  cylinder,  C.  The  dis- 
tribution of  steam  is  efiected  by  gridiron  slide-valves,  having  a 
short,  horizontal  movement  imparted  by  revolving  cams,  D, 
fixed  on  a  horizontal  shaft,  E,  running  along  the  bases  of  the 
cylinders,  and  driven  by  the  crank-shaft  through  suitable  gear- 
ing, F.  The  steam  is  cut  ofi"  by  the  further  revolution  of  the 
cam.  The  cut-off  is  adjustable,  and  controlled  by  the  gov- 
ernor, G. 

After  expanding  to  the  end  of  the  stroke  the  steam  passes 


58  MAIN   DRAINAGE    WORKS. 

through  the  exhaust  steam-chests  to  reheaters,  H.  These  are 
cast-iron  boxes,  each  contaming  about  750  |-inch  brass  tubes, 
two  feet  nme  mches  loiiir.  These  tubes  are  filled  with  hio-h- 
pressure  steam,  and  in  circulating  about  them  the  working 
steam  is  thoroughly  dried. 

From  the  reheaters  the  steam  is  admitted  to  the  low-pressure 
cylinder,  I,  where  further  expansion  takes  place.  Thence  it 
passes  to  the  condenser,  J,  where  it  is  condensed  by  salt  water 
from  a  rose  jet.  K  is  the  air-pump,  and  L  the  outboard 
delivery-pipe. 

The  pumps,  M,  are  hung  to  heavy  girders  supporting  the 
engines  by  cast-iron  hangers,  N.  A  part  or  the  whole  of  the 
weight  of  the  pumps  can  also  be  supported  by  the  wheels,  O, 
resting  on  very  strong  cast-iron  beams,  P,  built  into  the  ma- 
sonry on  either  side  of  the  pump-wells.  By  disconnecting 
their  hangers,  the  pumps,  supported  entirely  by  these  wheels, 
can  be  run  back  on  the  beams  (which  then  serve  as  tracks), 
and  can  be  hoisted  out  of  the  pump-wells  without  interfering 
with  the  fixed  parts  of  the  engine. 

At  Q  are  side  galleries,  through  either  of  which  the  sewage 
reaches  the  gateways,  K,  leading  into  the  pump-wells.  In  front 
of  these  gateways  are  iron  gates,  not  shown  on  the  plate,  which 
admit  or  exclude  the  sewage.  S  S  are  the  plungers.  TJ  U  are 
man-holes.  T  is  the  force-main.  The  discharo^e  from  one 
pump  passes  through  the  delivery-chamber  of  the  other. 

The  interior  construction  of  the  pump  is  shown  by  Fig.  1 
on  Plate  XIV.,  which  is  a  vertical  section  through  the  pump 
under  the  high-pressure  cylinder.  The  plunger  is  represented 
as  just  completing  its  down  stroke.  The  suction-valves  (of 
which  there  are  36  to  each  pump)  are  closed,  and  the  delivery- 
valves  (27  in  number)  are  wide  open,  to  permit  the  discharge 
of  the  sewage  displaced  by  the  plunger.  In  the  other  pump, 
at  the  same  moment,  the  plunger  would  be  completing  its  up- 
ward stroke,  and  the  action  of  the  valves  would  be  reversed. 

The  valves  are  of  somewhat  novel  construction,  and  are 
shown  by  a  section  of  a  portion  of  one  of  the  valve-plates  and 
the  whole  of  one  valve  (Plate  XIV.,  Fig.  2).  As  will  be  seen, 
they  are  simply  rubber  flaps,  |-inch  thick,  with  wrought-iron 


Plate;     XIII. 


rTjTnpmwmrmTTTTrnTia 


Plate  ZIV 


LEAVITT    PUMP 


WORTH INGTON    PUMP 

Fig.  3 


FRONT    ELEVATION 
PLAN 


TOP  BOTTOM 

FILTH    CAGES 


CITY    OF    BOSTON, 
MAIN     DRAINAGE. 

PUMPS  AND  FILTH    CAGES. 


PUMPING-STATION.  59 

backs  and  washer  plates,  the  rubber  faces  bearing  on  cast-iron 
seats  inclined  at  an  angle  of  45°.  The  valves  form  their  own 
hinges,  and  open  against  guards  or  stops  faced  with  leather. 
The  clear  opening  is  4^  x  13 2  inches.  Pieces  of  board  10 
inches  wide  and  24  inches  long  have  passed  through  these  valves. 

The  ordinary  working  duty  of  these  engines  is  nearly  or 
quite  100,000,000  foot-pounds  to  each  100  pounds  of  coal.^ 

The  two  pumping-engines  for  storm  service  were  built  at  the 
Hydraulic  AVorks,  Brooklyn,  L.I.,  by  the  firm  of  Henry  R. 
Worth ington,  of  New  York,  from  their  own  designs,  and  cost 
$45,000  each. 

They  are  of  the  Worthington  duplex,  compound,  condensing 
type.  Each  machine  consists  in  reality  of  two  distinct  com- 
pound engines  coupled  together,  each  engine  working  a  double- 
acting  plunger-pump.  The  capacity  of  each  double  engine  is 
25,000,000  gallons  of  sewage  a  day  raised  against  a  total  head 
of  43  feet.  This  requires  about  twelve  double  strokes  a  minute 
and  a  piston  speed  of  about  115  feet  per  minute. 

Steam  at  from  40  to  50  pounds  is  carried  full  pressure 
through  the  stroke  of  each  high-pressure  cylinder.  Thence  it 
passes  through  reheaters  to  the  adjoining  low-pressure  or  ex- 
pansion cylinders,  and  is  expanded  during  the  reverse  stroke.  It 
is  then  admitted  to  the  condenser  and  condensed  by  a  jet  of  salt 
water.  The  steam  cylinders  are  21  and  36  inches  in  diameter 
respectively.  They  are  steam-jacketed  all  over  and  suitably 
coated  and  lago-ed.     The  stroke  is  four  feet. 

The  steam-valves  are  moved  by  a  novel  and  ingenious  con- 
trivance, called  by  the  makers  "the  hydraulic  link."  Each 
engine  has  two  small  vertical  cylinders,  in  which  are  plungers 
w^orked  from  the  air-pump  bell-crank.  These  plungers  force 
water  forward  and  backward  through  pipes  leading  to  a 
cylinder  in  front  of  the  high-pressure    steam-chest.     In   this 

1  Two  duty  trials,  of  24  hours'  duration  each,  have  heen  made  recently  of  one  of  the 
Leavitt  pumping-engines.  These  tests  were  very  carefully  conducted,  and  all  fuel  burned 
under  the  boiler  was  charged,  no  deductions  being  made  for  ashes  and  clinkers.  In  the 
first  trial  steam  required  for  the  feed-pump  was  supplied  from  a  separate  boiler.  Making 
no  deduction  for  this,  the  duty  developed  was  a  little  over  123,000,000  foot-pounds  for 
each  100  pounds  of  coal.  In  the  second  trial  the  same  boiler  supplied  steam  for  the 
pumping-engine  and  the  feed-pump,  and  the  duty  developed  was  about  122,000,000  foot- 
pounds. 


60  MAIN   DRAINAGE   WORKS. 

cylinder  is  a  piston  connected  with  the  main  valve-stem  of  the 
engine,  and  the  pressure  imparted  by  the  water  alternately  to 
opposite  sides  of  the  piston,  moves  the  valve-stem  and  effects 
the  steam  distribution. 

There  are  two  pumps  to  each  machine.  Fig.  3,  Plate  XIY., 
is  a  section  through  the  pumps  of  one  engine.  Each  pump  is 
double-acting,  being  divided  transversely  in  the  middle  by  a 
ring  which  packs  the  plunger.  The  plunger  is  hollow,  45 
inches  in  diameter,  and  has  a  4-foot  stroke.  It  displaces  its 
bulk  of  sewage  at  each  stroke  in  either  direction.  The  positions 
of  the  valves,  suction  and  delivery  chambers  are  indicated  by 
the  section.  The  valves,  are  similar  to  those  of  the  Leavitt 
engines. 

The  engines  and  pumps  are  compact,  and  very  conven- 
iently arranged  for  inspection  of  all  their  parts.  A  fair  idea  of 
their  appearance  can  be  obtained  from  Plate  XV.,  which  is  a 
photograph  taken  inside  the  engine-house.  The  guaranteed 
duty  of  these  engines  is  60,000,000  pounds  of  sewage  raised  1 
foot  high  by  the  consumption  of  100  pounds  of  coal. 

To  supply  steam  for  the  four  engines  there  are  four  boilers, 
of  a  nominal  capacity  of  250  horse-power  each.  They  were 
built  by  Kendall  &  Eoberts,  of  Cambridge,  Mass.,  and  cost 
about  $9,500  each. 

The  boilers  are  of  the  horizontal  fire-box,  tubular  form,  and 
are  made  of  homogeneous  steel ,  having  a  tensile  strength  of  not 
less  than  60,000  pounds  per  square  inch,  an  elastic  limit  of 
37,000  pounds,  and  an  elongation  of  30  per  cent.  The  shell  is 
j5g-inch,  and  the  tube-sheets  are  ^-inch  thick.  The  length  over 
all  is  39  feet  10  inches.  There  are  132  tubes,  3-inch  internal 
diameter,  15  feet  long. 

Each  boiler  has  two  fire-boxes,  3^  feet  wide,  5  feet  high,  and 
11  feet  long.  At  the  ends  of  the  fire-boxes  is  a  combustion 
chamber  four  feet  long. 

The  smoke-flues  return  into  chambers  containing  flue-heaters, 
composed  of  80  seamless  brass  tubes,  2^  inches  in  diameter  and 
15  feet  lono'.  The  heaters  are  on  a  level  with  the  boiler-house 
floor,  and  can  be  run  out  from  their  chambers  for  cleaning  or  re- 
pairs. From  the  heaters  the  smoke  passes  by  brick  flues  under 
the  floor  to  the  chimney. 


Plate  XV. 


m 

c 

r; 

en 

a 


05 

c 

0 


03 

0 

c 
c 


Plate  XVfl. 


03 


CO 

r; 
'cO 
Q 


wm  ■ 


PUMPING-STATION.  61 

The  chimney  Las  a  circular  flue,  06  inches  internal  diameter 
and  140  feet  high. 

Among  the  minor  engines  and  pumps  appertaining  to  the 
pumping-station  are  four  engines  for  raising  and  lowering  the 
filth  cages ;  two  engines  for  moving  the  gates  in  the  engine- 
house  galleries ;  two  pair  of  double-acting  steam-pumps  for 
feeding  the  boilers  ;  two  double-acting  steam-pumps  for  supply- 
ing salt  water  to  the  condensers ;  one  large  steam-pump  for 
emptying  the  pump-wells  and  galleries  in  the  engine-house. 

The  buildings  are  warmed  by  a  system  of  steam-pipes  and 
radiators,  and  are  lighted  by  gas  made  on  the  premises  from 
gasoline. 

The  coal-house  is  129  X  59.5  feet  in  mternal  dimensions. 
It  contains  six  coal  bins,  or  pockets,  with  a  combined  capacity  of 
about  2,500  tons  of  coal.  These  bins  are  23  feet  high,  and  are 
built  with  solid  walls  formed  of  2  X  6  inch  spruce  lumber, 
planed  to  an  even  thickness,  and  spiked  flatwise  on  each  other, 
—  a  method  of  construction  similar  to  that  used  in  building  grain 
elevators.  The  coal-house  floor  is  made  of  Portland  cement 
concrete.  Iron  cars  are  used  for  bringing  coal  from  the  bins 
to  the  boilers,  and  suitable  tracks,  turn-tables,  and  scales  are 
provided. 

To  furnish  access  to  the  pumping-station  for  colliers  and 
other  vessels,  a  channel  one-half  of  a  mile  lono;  was  dredsfed  out 
to  the  ship-channel  in  Dorchester  Bay ;  380  feet  of  dock- wall 
and  a  wharf  280  feet  long  were  constructed.  To  facilitate  the 
unloading  of  coal  a  coal-run,  supported  on  a  trestle  27  feet  high, 
connects  the  wharf  with  the  coal-house,  and  extends  over  the 
tops  of  the  bins  within  the  house. 

Above  their  foundations  all  buildings  at  the  pumping-station 
were  designed  and  built  by  the  City  Architect's  Department. 
A  front  view  of  the  main  building  is  given  by  Plate  XVI 
(frontispiece) ,  and  a  side  view  by  Plate  XVII.  This  building 
cost  about  $300,000. 


62  MAESr   DRAINAGE   WORKS. 


CHAPTER  yni. 

OUTFALL    SEWER. 

The  sewage  is  pumped  through  48-inch  iron  force  mains 
(Plates  X.  and  XI.)  into  what  is  called  the  pipe-chamber.  At 
this  point  the  sewage  reaches  its  greatest  elevation,  and  is  high 
enough  to  flow  into  the  reservoir  at  Moon  Island.  The  pipe- 
chamber  is  a  granite  masonry  structure,  51  feet  long  inside, 
resting;  on  a  foundation  bed  of  concrete,  24  inches  thick. 
The  walls  are  21  feet  high,  from  4  to  7.5  feet  thick,  and  contain 
more  than  100  dressed  stones.  The  force  mains  from  the  four 
pumps  already  provided  pass  through  the  westerly  wall  of  the 
pipe-chamber,  and  four  more  short  sections  of  48-inch  pipes 
are  also  built  into  that  wall,  to  connect  finally  with  the  four 
additional  pumps,  which  it  is  expected  may  be  needed  in  the 
future. 

From  the  pipe-chamber  the  sewage  passes  into  what  are 
called  the  deposit  sewers,  and  through  them  flows  nearly  a 
quarter  of  a  mile  to  the  west  shaft  of  the  tunnel  under  Dor- 
chester Bay.  These  sewers  are  supported  and  protected  by  a 
gravel  pier,  or  embankment,  built  from  the  original  shore  line 
at  the  engine-house  out  to,  and  including,  the  tunnel  shaft. 
Plate  XVIIl.  gives  a  general  view  of  this  pier  from  its  outer 
end.  The  picture  is  a  reproduction  of  a  photograph  taken 
during  the  winter  when  the  bay  was  frozen  over.  A  cross- 
section  of  this  pier  is  shown  by  Fig.  5,  Plate  XIX.  It  is 
built  of  gravel,  which  was  mostly  dredged  from  the  harbor. 
On  its  northerly  or  most  exposed  side  the  pier  is  protected  by 
a  rip-rap  embankment,  ballasted  with  broken  stones  and  oyster- 
shells.  The  southerly  slope  is  ballasted  and  paved  with  stone, 
and  the  easterly  end  of  the  pier  is  protected  by  a  retaining- 
wall  (Fig.  4)  of  cut-stone  masonry,  laid  in  mortar  and 
backed  with  concrete,  the  whole  resting  on  a  pile  foundation. 
In  all  there  were  used  in  building  this  pier  about  41,000  tons 


Plate  XVIII. 


& 


m 


G 
0 
♦-) 
CO 
♦J 

(/] 

CD 
C 

a 
S 

0. 


OUTFALL    SE"\VER.  63 

of  rip-rap,  1G,000  yards  of  ballast,  120,000  yards  of  gravel, 
600  yards  of  dimension  stone,  and  650  piles.  The  pier  was 
built  l)y  contract,  and  its  total  cost,  excluding  that  of  the  sewer, 
was  $142,064.97. 

The  general  character  of  the  deposit  sewers  is  shown  by 
Fig.  7.  As  will  be  seen  they  consist  of  a  monolithic  struct- 
ure of  concrete,  forming  two  conduits,  each  16  feet  high  and  8 
feet  wide.  This  height  is  necessary  to  accommodate  the  daily 
variations  in  the  elevations  of  the  surface  of  the  sewage  due  to  fill- 
ing and  emptying  of  the  reservoir  at  Moon  Island.  The  sewers 
are  dammed  at  their  lower  ends  to  maintain  a  depth  of  from  8 
to  10  feet,  in  order  that  the  velocity  of  flow  through  them  may  be 
very  sluggish,  so  that  any  suspended  matters  may  be  deposited 
here  before  reaching  the  tunnel .  They  are  provided  with  gates 
and  grooves  for  stop-planks,  so  that  the  sewage  can  be  turned 
through  either  or  both  sewers,  and  either  can  be  entirely  emp- 
tied if  necessary. 

The  whole  structure  contains  about  10  cubic  yards  of  con- 
crete to  the  lineal  foot,  or  over  12,000  yards  in  all.  The 
bottom  portion  up  to  the  straight  walls  is  formed  of  Eosendale 
cement,  sand,  and  stone,  in  the  proportion  of  each,  respect- 
ively, of  1,  2  and  5.  Above  this  elevation,  for  the  outer  side 
walls,  the  same  proportion  is  maintained ;  but  the  cement  used 
was  a  mixture  of  1  part  Portland  and  2  parts  Rosendale. 
For  the  concrete  forming  the  centre  wall  and  top  arches  only 
Portland  cement  was  used.  The  best  Rosendale  and  very  fine 
ground  Portland  cement  were  procured  for  the  work.  The 
sand  was  screened  on  the  spot  from  the  gravel  forming  the  pier, 
and  a  portion  of  the  stone  was  obtained  in  a  like  manner.  A 
still  larger  proportion  of  the  stone  came  from  the  tunnel  exca- 
vation, being  brought  in  lighters  from  the  middle  shaft  and 
passed  through  a  stone-crusher.  Machine  concrete  mixers 
were  used,  into  which  the  cement,  sand,  and  stones,  in  proper 
proportions,  were  continuously  shovelled. 

The  concrete  was  rammed  thoroughly  in  6-inch  courses. 
Long  sticks  of  timber  were  embedded  in  each  layer  of  concrete 
while  it  was  being  rammed  into  place,  and  were  removed  after 
it  had  set,  and  before  the  next  layer  was  added.     The  spaces 


64  MAIN   DRAINAGE    WORKS. 

occupied  by  the  sticks  formed  grooves,  into  which  the  succeeding 
layers  bonded.  In  cutting  through  one  side  of  this  structure  six 
months  after  its  completion  the  whole  mass  was  found  to  be 
perfectly  homogeneous,  and  lines  of  demarcation  between  the 
different  layers  could  not  be  detected. 

The  bottoms  of  the  sewers  are  lined  with  one  layer  of  hard- 
burned  bricks  to  resist  erosion  when  the  sewers  are  cleaned. 
The  sides  are  plastered  with  a  |^-inch  coat  of  Portland  cement 
mortar.  The  arches  are  of  long  radius  and  but  13  inches  thick. 
As  they  were  to  be  loaded  at  once,  they  were  tied,  as  shown,  by 
l|^-inch  wrought-iron  rods,  spaced  five  feet  apart.  Brick  man- 
holes were  built  at  intervals  of  300  feet. 

Comparatively  heavy  matters,  such  as  gravel  and  sand,  settle 
almost  at  once  at  the  west  end  of  the  deposit  sewers.  Lighter 
matters  travel  a  little  further ;  but  only  a  very  light  semi-fluid 
precipitate  is  ever  found  at  the  easterly  end  of  the  sewers,  near 
the  shaft. 

The  best  way  to  clean  out  this  deposit  was  long  considered, 
and  the  following  plan  was  finally  adopted.  A  large  wooden 
tank  was  built  near  the  end  of  the  pier,  just  outside  of  its 
southerly  slope,  about  120  feet  distant  from  the  sewers  (Figs. 
3,  5,  and  6,  Plate  XIX.).  It  is  supported  on  piles,  its  floor 
beino-  three  feet  above  high  water  and  one  foot  lower  than  the  bot- 
toms  of  the  sewers.  One  end  of  this  tank  is  connected  with  the 
deposit  sewers  by  two  6-inch  iron  pipes,  the  other  end  is  con- 
nected with  the  chamber  about  the  tunnel-shaft  by  a  12-inch 
pipe.  By  means  of  stop-planks  the  surface  of  water  is  made  to 
stand  about  three  feet  higher  in  the  deposit  sewers  than  it  does 
in  the  shaft-chamber.  Circulation  is  thus  established  from  the 
deposit  sewers  through  the  6-inch  pipes  into  the  tank,  and 
thence  through  the  12-inch  pipe  to  the  shaft,  and  a  part  of  the 
sewage  goes  to  the  tunnel  through  this  by-pass. 

The  6-inch  pipes  leave  the  deposit  sewers  near  their  bot- 
toms, and  the  sewage  which  enters  the  pipes  draws  sludge  along 
with  it  and  again  deposits  it  in  the  still  water  of  the  tank.  The 
tank  is  10  feet  wide,  15  feet  high,  and  50  feet  long,  and  will 
hold  about  150  yards  of  sludge.  It  has  on  its  seaward  side 
three  gate-openings,  terminating  in  cast-iron  nozzles,  12  inches 


SECTIONAL    PLAN  ON   LINES   E.F.G.H.K.L. 
FIG. I 


CITY    or    BOSTON 

MAIN  drainage: 

OUTFALL  SEWER 


CHAMBER    CONNECTING    DEPOSIT    SEWERS 
WITH  WEST   SHAFT    Of    TUNNEL 


SECTIONAL  ELEVATION  ON  LINES  A.B.C.D. 
riG.  2 


OLD  HARBOR  PIER  PLAN  AT  END. 
FIG.  3 


OLD  HARBOR  PIER  CROSS  SECTION. 
FIG.  5 


TRANSVERSE  SECTION  OF  DEPOSIT  SEWERS     LONG. SECTION  OF  DEPOSIT  SEWER 
AND  END  VIEW  OF  SCRAPER.  SHOWING  SCRAPER. 

FIG. 7  FIG. 8 


OUTFALL   SEWER.  65 

in  diameter.  When  the  tank  is  full  of  sludge  a  scoav  is  laid 
alongside  it,  and  the  nozzles  are  connected  with  the  interior  of 
the  scow  by  means  of  canvas  tubes.  The  gates  are  then  opened, 
and  the  sludge  flows  from  the  tank  into  the  scow. 

In  order  to  draw  down  to  the  6-inch  pipes  the  sludge  which 
has  been  deposited  at  the  upper  ends  of  the  deposit  sewers 
scrapers  are  used.  These  consist  of  floating  rafts  (Figs.  7  and 
8,  Plate  XIX.),  made  of  12-inch  hollow  iron  tubes,  to  the  bot- 
toms of  which  are  hung  wooden  aprons,  a  little  less  wide  than 
the  sewers.  The  aprons  are  weighted  so  that  their  lower  edges, 
which  are  provided  with  broad  iron  teeth,  sink  somewhat  into 
the  sludge.  The  current  in  the  sewers  carries  the  whole 
apparatus  down  stream,  and  the  sludge  is  scraped  and  flushed 
before  it. 

The  deposit  sewers  connect  with  the  tunnel  shaft  at  a  masonry 
chamber  built  about  the  latter  (Figs.  1  and  2,  Plate  XIX.). 
At  the  ends  of  the  sewers  are  placed  gates  7X8  feet  in  size. 
These  gates  maintain  a  depth  of  eight  or  more  feet  in  the  sewers. 
They  are  so  arranged  that  on  tripping  a  latch  they  can  swing 
open  and  empty  suddenly  the  liquid  contents  of  the  sewers  into 
the  tunnel,  producing  temporarily  a  strong  flushing  velocity. 
Immediately  about  the  shaft  is  a  wrought-iron  cage ,  to  prevent 
any  bulky  object  w^hich  may  fall  into  the  sewers  from  reaching 
the  tunnel. 

The  shaft  chamber  is  encircled  by  two  6|-feet  "  waste  sewers," 
into  which  the  deposit  sewers  can  overflow  above  waste  weirs, 
or  with  which  they  can  directly  connect  instead  of  discharging 
into  the  tunnel.  The  waste  sewers  unite  just  east  of  the  shaft- 
chamber  and  pass  to  an  outlet  built  through  the  sea-wall  at  the 
end  of  the  pier.  Should  the  tunnel  ever  be  emptied  for  inspec- 
tion sewage  can  temporarily  be  pumped  into  Dorchester  Bay 
throuirh  this  outlet.  Above  the  shaft  chamber  is  a  brick  o-ate- 
house  of  ornamental  design,  built  by  the  City  Architect. 

The  second  section  of  outfall  sewer  comprises  the  tunnel 
under  Dorchester  Bay.  Exploratory  borings  made  on  the 
tunnel  line  during  the  preliminary  survey  showed  that  the  sur- 
face of  bed  rock  was  but  little  below  the  bottom  of  the  harbor, 
fi'om  Squantum  to  aljout  the  middle  of  the   bay.     From  that 


6Q  MAIN    DRAINAGE    WORKS. 

point  westwardly  towards  Old  Harbor  Point  the  rock  dipped 
rapidly,  so  that  under  the  pumping-station  its  surface  is  214 
feet  below  the  surface  of  the  ground.  The  surface  of  the  rock 
is  somewhat  shaken,  and  immediately  above  it  is  a  water-bearing 
stratum  of  sand,  gravel,  and  boulders.  Above  this,  clay  extends 
nearly  to  the  harbor  bottom,  which  is  composed  of  a  bed  of  mud 
of  varying  thickness. 

The  clay  is  of  uniform  character,  and  contains  occasional 
veins  and  pockets  of  sand.  Using  reasonable  precautions  a 
tunnel  could  be  safely  and  expeditiously  built  in  it.  The  per- 
vious stratum  over  the  rock  and  the  demoralized  upper  portion 
of  the  rock  itself  were  not  at  all  favoral)le  for  tunnelling  opera- 
tions, and  could  only  have  been  penetrated  with  extreme  pre- 
caution and  a  considerable  chance  of  ftiilure.  The  rock  itself 
was  well  adapted  for  tunnelling.  It  consists  of  a  succession  of 
clay-slates  and  conglomerates,  and  belongs  to  the  series  known 
as  the  Roxbury  "pudding-stone"  beds. 

When  the  trough  in  which  these  beds  lie  was  formed  they 
were  subjected  to  great  pressures,  which  crumpled  and  tilted 
them,  and  produced  many  faults,  fissures,  and  joint  planes. 
The  fissures  were  filled  solidly  from  below,  and  few  shrinkage 
seams  were  found  sufficiently  open  for  the  passage  of  water 
from  above.  The  existence  of  the  joint  planes,  especially  in 
the  clay-slates,  greatly  fiicilitated  the  breaking  and  removal  of 
the  rock. 

As  at  first  designed,  the  tunnel  was  to  start  from  a  shaft  100 
feet  deep  at  Old  Harbor  Point  and  be  built  in  the  clay  for  about 
2,100  feet,  when  it  would  enter  the  rock  and  continue  in  it  to 
its  end,  at  Squantum.  Further  consideration  of  the  difficulty 
and  possible  danger  of  passing  gradually  from  soft  ground  into 
rock,  and  of  tunnelling  for  several  hundred  feet  wholly  or 
partly  through  very  wet  and  loose  material,  led  to  locating  the 
west  shaft  at  such  a  distance  from  the  shore  that  rock  could  be 
reached  at  a  practicable  depth  and  the  tunnel  could  be  safely 
built  wholly  within  it. 

The  average  elevation  of  the  tunnel  is  142  feet  below  low 
water  (Plate  XX.,  Fig.  1).  The  total  length  through  which 
the  sewage  flows  is  7,160  feet.     Of  this  distance  149  feet  is  in 


OUTFALL   SEWER.  67 

the  west  shaft,  6,088  feet  is  nearly  horizontal  between  the  west 
and  cast  shafts,  and  923  feet  is  in  the  inclined  portion  leading 
from  the  bottom  of  the  east  shaft  to  the  end  of  the  tunnel,  on 
Squantum  Xeck. 

To  facilitate  construction  there  were  three  working  shafts 
about  3,000  feet  apart. 

The  tunnel  was  built  under  a  contract  which  was  drawn  with 
great  care.  The  contractor  was  first  to  build,  in  accordance  with 
plans  furnished,  three  timber  bulkheads,  or  piers,  to  protect 
the  shafts.  Inside  of  these  bulkheads  he  was  to  sink  iron 
cylinders,  constituting  the  upper  portions  of  the  shafts.  These 
c^dinders  were  paid  for  by  the  lineal  foot,  and  the  contractor 
was  permitted  and  required  to  build  as  much  of  the  shafts  as 
possible  in  this  way,  loading  and  forcing  the  iron  to  the  greatest 
■attainable  depth.  Below  the  cylinders  the  shafts  could  be  ex- 
cavated of  any  desired  size  and  shape.  The  tunnel,  also,  could 
be  excavated  of  any  size,  provided  that  both  it  and  the  shafts 
were  finally  lined  with  a  7^-  feet  diameter  circular  shell  of  brick 
work,  12  inches  thick,  backed  with  brick  or  concrete  masonry 
to  the  sides  of  the  excavation.  Bricks  and  cement  were  to  be 
purchased  from  the  city  at  stipulated  prices.  The  completed 
tunnel  was  to  be  paid  for  at  the  proposed  price  per  lineal 
foot. 

Great  stress  was  laid  upon  the  precautions  to  be  adopted  to 
prevent  delay  and  damage  arising  from  an  influx  of  water  into 
the  shafts.  Appliances  to  control  any  such  influx  were  to  be 
kept  in  readiness,  and,  should  these  prove  insufficient,  the  ple- 
num process,  or  use  of  compressed  air  within  the  shafts,  was  to 
be  resorted  to. 

The  work  was  let  Oct.  29,  1879,  and  the  contractor  at  once 
proceeded  with  the  building  of  the  bulkheads.  These  were  alike, 
and  consisted  (Fig.  2,  Plate  XX.)  of  wooden  boxes  20  feet 
square  inside,  formed  of  large  oak  piles,  driven  two  feet  on 
centres,  capped  and  braced  with  hard-pine  sticks,  and  tied 
diagonally  at  the  corners  with  2-inch  iron  bolts.  The  boxes 
were  lined  inside  with  4-inch  tongued  and  grooved  sheet-piling, 
and  the  spaces  between  the  sheet  planks  and  cylinders  were 
filled  with  puddled  clay.     The  tops  of  the  bulkheads  were  eight 


68  MAIN    DRAINAGE    WORKS. 

feet  above  mean  high  water,  and  the  contract  price  for  them 
was  $2,500  apiece. 

Having  completed  the  bulkheads  the  cylinders  were  sunk 
inside  of  them.  Each  cylinder  (Plate  XX.,  Fig.  3)  consisted 
of  a  circular  shell  of  cast  iron,  9.5  feet  inside  diameter,  with  1| 
inches  thickness  of  metal.  They  were  cast  in  sections,  five 
feet  long,  and  united  by  l^-inch  bolts  passing  through  inside 
flanges.  The  abutting  ends  of  the  sections  were  faced,  and  the 
bolt-holes,  of  which  there  were  30  in  each  flange,  were  drilled 
to  a  templet,  so  that  the  sections  were  interchangeable.  The 
bottom  section  of  each  cylinder  had  its  lower  10  inches  cham- 
fered off  to  a  cutting  edge.  The  contract  price  for  furnishing 
the  cylinders,  which  weighed  a  ton  to  the  foot,  was  $88  per 
lineal  foot. 

At  the  east  and  middle  shafts  the  cylinders  were  easily 
forced  down  to  the  rock,  at  depths  below  the  surface  of  the 
ground  of  21  and  38  feet  respectively.  It  was  known  that  it 
would  be  impossible  to  drive  the  cylinder  at  the  west  shaft  down 
to  the  rock.  By  weighting  it  with  about  180  tons  of  iron  dross 
it  was  finally  forced  into  the  clay  to  a  depth  of  about  60  feet 
below  the  harbor  bottom.  Below  this  point  a  square  shaft,  10 
feet  across,  was  excavated  with  great  ease  in  plastic  clay,  pene- 
trated with  occasional  veins  of  fine  sand,  but  yielding  little 
water  (Plate  XXI.,  Fig.  1). 

The  timbering  of  this  shaft  was  hastily  and,  as  it  seemed  to 
the  engineers,  carelessly  done,  the  timbers  being  insecurely 
braced,  and  cavities  being  continually  left  outside  of  them. 
The  engineer  in  charge  consulted  the  City  Engineer  as  to  the 
possibility  of  requiring  greater  caution  in  doing  this  work.  It 
was  decided,  however,  that  the  spirit  of  the  contract  would  not 
permit  interference  with  the  contractor's  method  of  building  this 
portion  of  the  shaft. 

No  difficulty  was  encountered  until  the  rock  was  neared,  when 
water,  to  the  amount  of  10,000  gallons  an  hour,  broke  in  from 
below,  and,  no  provision  having  been  made  for  its  removal,  filled 
the  shaft.  Pumps  were  obtained  and  the  shaft  emptied,  when 
it  was  found  that  the  water,  following  the  cavities  behind  the 
lining,  had  softened  the  clay  and  loosened  the  timbering,  so  that 


CITY    OF    BOSTON  -  MAIN    DRAINAGE. 
OUTFALL   SEWER.  DORCHESTER    BAY    TUNNEL. 


LONGITUDINAL     SECTION     OF     TUNNEL 

FIG.  I. 


'T^° 


SIDE     ELEVATION 


HALF    SECTION  HALF    PLAN 


BULKHEADS     ABOUT     SHAFTS 

FIG,  a. 


IRON      CYLINDERS 
FIG.  3. 


OUTFALL    SEWER.  69 

it  was  in  very  bad  shape.     About  40  feet  in  length  of  the  shaft 
had  to  be  retinibered,  the  ohl  sticks  being  cut  out  with  chisels. 

This  work  was  not  accomplished  without  great  difficulty. 
Although  the  quantity  of  water  to  be  dealt  with  was  not  great, 
the  cramped  dimensions  of  the  shaft  afforded  little  room  for 
the  pumps,  or  opportunity  for  supporting  them.  When  these 
gave  out,  as  they  occasionally  did,  the  shaft  filled  w^ith  water, 
causing  considerable  delay  and  damage.  To  counteract  a 
downward  pressure  exerted  by  the  clay  upon  the  timber  lining, 
a  portion  of  it  was  suspended  by  heavy  wire  cables  from  the 
cylinder  above.  During  all  these  operations  the  whole  shaft, 
including  timbered  portion  and  cylinder,  also  the  surrounding 
clay  and  the  bulkhead  above,  were  in  motion,  settling  slowly. 
By  the  time  the  shaft  had  l)een  iirmly  founded  on  the  rock  the 
pile  bulkhead  had  settled  nearly  five  feet. 

After  the  shafts  had  been  sunk  and  secured  the  excavation 
for  the  tunnel  proper  encountered  no  serious  obstacles.  The 
work  was  carried  on  at  six  diiferent  headings.  From  the  mid- 
dle and  east  shafts  work  progressed  in  both  directions,  and 
from  the  west  shaft  and  the  upper  end  of  the  incline  at  Squan- 
tum  single  headings  w-ere  driven. 

The  incline  descends  one  foot  vertical  in  six  feet  horizontal. 
At  this  ponit  a  heading  was  driven  downwards  for  about  400 
feet  and  then  stopped,  owing  to  the  difficulty  and  expense  of 
removing  the  water  which  accumulated  at  its  face.  At  the 
middle  shaft  power  drills,  driven  by  compressed  air,  were  used, 
and  at  other  points  hand  drilling  was  employed. 

There  was  not  much  difi^erence  as  to  either  expense  or  rapid- 
ity in  the  two  methods.     By  either  an  advance  of  four  feet  was 
considered  a  fair  day's  work.     The  chief  merit  of  the  air  drills 
seemed  to  be  that  they  were  not  demoralized  by  pay-days,  and* 
never  struck  for  higher  wages. 

Various  forms  of  nitro-glycerine  were  employed  as  explo- 
sives, and  no  casuality  occurred  through  its  use.  The  average 
diameter  of  the  excavation  (Plate  XXL,  Fig.  2)  was  about  10.2 
•  feet,  approximating  very  well  to  the  9.5  feet  required  to  receive 
the  final  In-ick  lining.  The  excavated  material,  amounting  to 
about   25,000  yards  in   all,  was  deposited  around  the  shafts, 


70  MAIN    DRAINAGE    WORKS. 

formino^  small  islands.     The  maximum  amount  of  water  leaking^ 
into  the  tunnel  at  any  time  was  64,000  gallons  an  hour. 

The  headings  between  the  east  and  middle  shafts  met  Jan. 
24,  1882,  and  those  between  the  middle  and  west  shafts  met 
June  22,  1882.  Lining  the  excavation  with  brick-work  began 
March  10,  of  the  same  year.  Projecting  portions  of  rock  were 
first  trimmed  off,  so  that  room  for  a  solid  brick  lining,  12  inches 
thick,  laid  in  courses,  could  always  be  obtained.  Kosendale 
cement  mortar  was  used,  composed  of  equal  parts  of  cement  and  . 
sand.  All  spaces  between  the  coursed  lining  and  the  sides  of 
the  rock  excavation  were  solidly  filled  with  masonry,  principally 
brick-work.  The  amount  of  backing  thus  required  to  make  solid 
work  averaged  about  three-fourths  of  a  yard  per  lineal  foot.  Fig. 
5,  Plate  XXI.  is  a  section  of  the  tunnel  at  the  point  of  maximum 
size  where  the  largest  amount  of  backing  was  needed.  In  all, 
7,416,000  bricks  and  23,377  barrels  of  cement  were  used  in 
building  the  tunnel.  About  12  lineal  feet  of  tunnel  could  be 
completely  lined  in  24  hours,  at  any  one  point. 

In  putting  in  the  lining,  iron  pipes  were  built  into  the  brick- 
work (Plate  XXI.,  Fig.  3)  wherever  necessary  to  furnish  out- 
lets for  the  water,  which  would  otherwise  have  washed  out  the 
mortar.  Some  of  these  pipes  were  afterwards  plugged,  but 
most  of  them  were  left  open.  The  pressure  of  the  water  when 
kept  from  entering  the  tunnel  was  about  64  pounds  per  square 
inch,  and  it  was  not  practicable  to  build  brick  masonry  which 
should  be  water-tight  under  such  a  pressure.  When  the  tunnel 
is  in  use  the  pressure  of  the  sewage  within  it  is  somewhat 
greater  than  that  of  the  water  outside  the  lining,  so  that  leak- 
age would  be  outwards,  except  that  the  particles  in  the  sewage 
will  quickly  clog  any  fine  holes  in  the  masonry. 

Some  experiments  were  made  to  determine  to  what  extent 
the  porosity  of  the  brick  lining  could  be  destroyed  by  silting 
from  without.  An  iron  pipe  extending  up  the  east  shaft  was 
connected  at  its  lower  end  with  the  pipes  built  through  the 
brick-work,  and  water  containing  clay,  cement,  and  fine  sawdust 
was  forced  outside  the  lining. 

The  finer  portions  of  these  materials  came  through  holes  and 
cracks  in  the  joints  of  the  masonry.    Fine  holes  were  thus  filled 


Plate   XXI. 


BOSTON   MAIN    DRAINAGE. 
DORCHESTER    BAY   TUNNEL. 


EAN    HIGH   WATER 


AVERAGE   SECTION   OF  TUNNEL 


TUNNEL    bECTION 
AT   POINT  OF   MAXIMUM    EXCAVATION 


OUTFALL   SEWER.  71 

and  leaknije  throuo^h  them  prevented.  Holes  of  apparent  size 
were  calked  with  lead.  By  these  means  the  leakage  into  the 
inclined  portion  of  the  tunnel  was  reduced  from  2,200  to  500 
gallons  an  hour.  It  was  not,  however,  considered  practicable, 
except  at  considerable  expense,  thus  materially  to  reduce  the 
leakage  ;  and,  in  view  of  its  slight  importance  in  respect  to  the 
use  of  the  tunnel,  the  attempt  was  given  up. 

The  west  shaft  was  lined  with  brick-work.  The  middle  shaft 
was  abandoned,  its  only  purpose  having  been  to  facilitate  con- 
struction. The  arch  of  the  tunnel  where  it  passes  under  this 
shaft  Avas  made  three  feet  thick,  and  a  counter  arch,  two  feet 
thick,  was  built  over  it  to  resist  upward  pressure,  in  case  the 
tunnel  should  ever  l)e  filled  suddenly  after  having  been  pumped 
out  for  any  purpose.  The  shaft  itself  was  not  filled  up,  but 
near  its  top  an  arch  was  built  to  prevent  any  heavy  substance 
ever  falling  down  it  (Plate  XXI.,  Fig.  4). 

The  east  shaft  was  lined  throughout.  A  large  Cornish  min- 
ing pump  has  been  purchased,  and  is  to  be  set  up  at  this  shaft 
as  soon  as  certain  legal  complications  affecting  the  city's  right 
to  the  location  shall  have  been  settled.  This  pump  will  have 
sufficient  capacity  to  empty  the  tunnel,  including  the  leakage 
into  it,  within  48  hours.  It  is  to  be  set  up  as  a  precaution,  as 
it  did  not  seem  wise  to  leave  any  portion  of  the  work  entirely 
inaccessible.  Should  the  tunnel  ever  be  pumped  out  at  this 
point  it  would  first  be  filled  with  salt  water,  so  that  no  possible 
nuisance  could  be  created  by  the  operation. 

A  sump,  or  well-hole,  seven  feet  deep,  from  which  to  pump,  was 
built  under  the  east  shaft  (Plate  XXL,  Figs.  6  and  7).  Pairs 
of  cast-iron  beams  were  built  into  the  lining  from  the  bottom  of 
the  shaft  to  its  top.  To  these  are  bolted  two  sets  of  upright 
iron  guides.  One  set  of  these  will  hold  in  place  the  rising  col- 
umn of  the  pump,  and  the  other  set  will  serve  for  an  elevator, 
to  be  used  in  visiting  the  pump  and  tunnel. 

It  Avas  thought  that  should  deposits  occur  in  the  tunnel,  they 
might  be  removed  by  passing  a  ball,  somewhat  smaller  in  diame- 
ter than  the  tunnel,  through  it.  To  guide  this  ball  past  the  east 
shaft,  four  wooden  guides,  suitably  shaped,  were  built  in  place 


72  MAIN    DRAINAGE    WORKS. 

at  that  point.  Appliances  for  handling  such  a  ball  were  pro- 
vided at  the  two  ends  of  the  tunnel. 

The  tunnel  was  practically  finished  July  25,  1883.  Its  com- 
pletion required  the  removal  of  all  elevators,  pumps,  pipes,  etc., 
used  in  constructing  it  and  the  closing  up  with  masonry  of  all 
pump-wells,  except  the  one  before  referred  to,  at  the  east  shaft. 
This  work  was  attended  with  considerable  anxiety,  as  the  pump- 
ino"  capacity  of  the  three  shafts  was  but  little  more  than  was 
necessary  to  control  the  leakage  of  water. 

The  finishing  and  removals  were  successfully  accomplished 
by  systematic  and  careful  management.  The  last  shaft  to  be 
cleared  was  the  east  shaft,  and  it  was  necessary  to  isolate  it  from 
the  rest  of  the  tunnel  by  a  timber  bulkhead,  behind  which  the 
water  entering  the  tunnel  accumulated  while  the  pumps  and 
their  appurtenances  were  being  removed.  By  the  time  the  shaft 
was  clear  the  tunnel  was  two-thirds  full  of  water.  The  bulk- 
head was  so  made  and  fastened  in  place  that  on  tripping  a  catch 
it  fell  apart  into  three  pieces,  which  were  hauled  out  by  ropes 
attached  to  them. 

The  contract  price  for  the  shafts,  exclusive  of  iron,  was  $86, 
and  for  the  tunnel  $48,  per  lineal  foot.  The  contractor  lost 
money,  and  after  about  two  years  abandoned  his  contract, 
alleo;ing  his  inability  to  complete  it  for  the  prices  therein  stipu- 
lated. He  ofiered  to  complete  the  tunnel  for  prices  about  one- 
half  greater  than  those  before  agreed  upon.  Considering  that 
he  had  the  requisite  plant  on  hand,  and  had  acquired  valuable 
experience  concerning  the  character  of  the  work  and  the  best 
methods  of  conducting  it ;  and  also  considering  that  the  bad 
reputation  which  the  tunnel  would  have,  if  abandoned,  would 
probably  deter  other  bidders  from  making  reasonable  offers,  — 
it  was  thought  for  the  best  interests  of  the  city  to  make  a  second 
ao:reement  with  the  same  contractor,  which  was  accordingly 
done.  The  final  total  cost  of  this  section  of  work,  including 
inspection  and  all  incidental  expenses,  was$658,489.97,  amount- 
ing to  about  $92  per  lineal  foot  of  tunnel. 

The  methods  of  alignment  employed  by  the  engineers  in 
immediate  charge  of  the  tunnel,  while  not  entirely  novel,  may 
be  of  sufficient  interest  to  be  mentioned.     The  west  shaft  was 


OUTFALL    SEWER.  73 

out  of  plumb,  so  that  by  droppinj::^  plumb-linos  a  base  only  5.7 
feet  long  could  be  obtained.  This  by  itself  would  have  made  accu- 
rate alio-nments  tedious.  Moreover,  each  shaft  contained  about 
six  lines  of  steam,  water,  and  exhaust  pipes,  besides  guides  for 
its  cage.  As  the  shafts  were  160  feet  deep,  were  dripping  with 
water,  and  had  currents  of  air  produced  by  hot  pipes  and  leak- 
ages of  steam,  it  would  have  been  necessary  to  protect  plumb- 
lines  by  tubes  for  the  whole  depth  of  the  shafts.  At  the  west 
shaft  it  would  have  been  impracticable  to  use  such  tubes,  as 
they  would  have  been  directly  in  the  way  of  the  cage. 

On  account  of  the  difficulty  attending  the  use  of  plumb-bobs, 
the  line  was  transferred  below  by  means  of  a  large  transit 
instrument  set  up  at  the  top  of  the  shaft.  The  telescope, 
having  been  set  on  line,  was  directed  down  the  shaft,  and  a  fine 
string,  extending  about  100  feet  into  the  tunnel,  was  ranged  in 
line.  The  string  was  illuminated  by  light  reflected  from  a 
mirror  placed  beneath  it.  Communication  between  the  engi- 
neers at  the  top  and  at  the  bottom  of  the  shaft  was  maintained 
by  the  use  of  hand  telephones. 

At  first  the  line  within  the  tunnel  was  produced  by  means  of 
instruments  ;  but,  as  the  headings  advanced,  the  ventilation  be- 
came so  bad  that  at  times  a  light  distant  only  75  feet  could  not 
be  seen.  The  line  was  then  produced  by  stretching  a  stout 
linen  thread,  about  600  feet  lono;,  and  takino;  ofi*sets  to  it.  The 
success  attending  these  methods  of  alignment  was  very  gratify- 
ing, as  the  headings  met  without  appreciable  error. 

Should  a  "high-level"  intercepting  sewer  ever  be  built  to 
conduct  a  part  of  the  city's  sewage,  by  gravitation,  to  Moon 
Island,  it  is  expected  that  it  will  join  the  present  system,  on 
Squantum  Neck,  at  the  further  end  of  the  tunnel.  To  provide 
for  such  a  contingency  the  present  outfall  sewer  is  much 
increased  in  size  beyond  this  point,  being  11  X  12  feet  in  dimen- 
sions. 

The  connection  between  the  tunnel  and  the  outfall  sewer 
beyond  is  made  in  an  underground  chamber  (Fig.  1,  Plate 
XXII.).  From  this  chamber,  also,  branches  a  short  section  of 
sewer  with  which  to  connect  the  future  "high-level "  system, 
should  it  ever  be  built.     The  chamber  is  covered  by  a  substan- 


74  MAIN   DRAINAGE   WORKS. 

tial  brick  building,  and  a  flight  of  stone  steps  leads  to  a  land- 
ing in  the  sewer  below.  The  floor  of  the  building  is  supported 
on  iron  beams,  and  can  be  taken  up  so  that  boats  can  be  low- 
ered into  the  sewer,  and  a  flushing-ball  can  be  taken  out.  To 
facilitate  these  operations  the  roof  was  made  exceptionally 
strong,  and  from  it  was  hung  an  iron  track  supporting  a  traveller 
and  blocks  capable  of  lifting  five  tons. 

As  far  as  the  easterly  shore  of  Squantum  Neck  the  outfall 
sewer  (Figs.  4,  6  and  7,  Plate  XXII.)  was  built  partly  in  rock 
excavation  and  partly  in  embankment.  In  the  latter  case  the 
sewer  is  tied  through  its  arch  by  l|-inch  iron  rods,  8  feet  apart. 
These  are  designed  to  prevent  the  possibility  of  distortion,  due 
to  movements  of  the  bank  below  the  sewer,  or  on  the  side  of 
it.  The  ties  will,  doubtless,  rust  out  in  time,  but  not  before 
the  need  of  them  is  over. 

From  Squantum  to  Moon  Island  an  embankment  (Plate 
XXII.,  Fig.  5)  was  built.  It  is  a  mile  long,  from  20  to  30 
feet  high,  20  feet  wide  on  top,  and  about  120  feet  at  its  base. 
Up  to  the  established  sewer  grade  the  embankment  was  chiefly 
built  of  dr^ds^ed  o-ravel,  and,  above  that  heio-ht,  of  material  ob- 
tained  in  excavating  for  the  reservoir  on  Moon  Island.  Up  to 
six  feet  above  high  water  the  slopes  are  protected  by  ballast 
and  rip-rap.  In  all,  about  141,000  yards  of  dredged  gravel, 
260,000  yards  of  other  earth,  20,000  yards  of  ballast,  and 
54,000  tons  of  rip-rap  were  used  in  building  the  embankment. 

About  4,100  feet  in  length  of  the  site  of  the  embankment 
consisted  of  beds  of  mud,  from  10  to  40  feet  deep.  It  was 
hoped  that  the  filling  would  displace  this  mud  and  reach  hard 
bottom.  It  did  so  at  a  few  points,  but  not  as  a  rule.  As  an 
Experiment  an  attempt  was  made  to  assist  this  action  by  explod- 
ing dynamite  cartridges  under  the  embankment.  No  results  of 
importance  were  thus  obtained ;  but  the  experiment  demon- 
strated the  resistance  of  the  mud  to  displacement  and  the  prob- 
able future  stability  of  the  embankment. 

Broad  plates,  with  vertical  iron  rods  fastened  to  them,  were 
placed  near  the  bottom  of  the  bank  on  its  centre  line,  and  the 
amount  of  settlement  as  filling  progressed  was  noted.  After 
the  bank  was  completed  slight  settlements  still  continued.     It 


Plate    XXII. 


CONNECTION-    CHAMBER. 


EMBANKMENT    BETWEEN    SQUANTUM  AND  MOON   ISLAND 

rig.5 


^    m 


J 


Fig.  6 
SECTION    IN   EMBANKMENT. 


SECTION   IN   EXCAVATION. 


BOSTON    MAIN     DRAINAGE 
OUTFALL  SEWER 


%. 


Fig.  7 


OUTFALL    SEWER.  75 

was,  therefore,  thought  more  prudent  to  postpone  huilding  a 
masonry  structure  for  some  years,  or  until  there  was  assurance 
that  the  bank  had  assumed  a  condition  of  permanent  stability. 

For  temporary  use  therefore,  a  wooden  flume  (Fig.  2,  Plate 
XXII.)  was  sul)stituted  for  the  masonry  sewer  at  this  point. 
The  flume  is  located  outside  of  the  emljankraent,  and  200  feet 
south  of  it.  It  is  supported  on  piles,  in  bents  ten  feet  apart, 
generally  with  three  piles  to  the  bent.  In  all,  al)Out  1,300  piles 
were  driven,  some  of  them  to  a  depth  of  40  feet. 

The  flume  proper  consists  of  a  square  wooden  l)ox,  six  feet  in 
diameter.  Its  sides,  top,  and  bottom  are  formed  of  Canadian 
Avhite  pine,  three  inches  thick,  planed  all  over.  The  planks, 
except  a  single  filling  in  course  on  each  side,  are  all  of  even 
width,  so  as  to  allow  breaking  joint.  They  are  grooved  on 
each  edge,  and  also  on  their  ends  (Fig.  3),  for  1^  X  |-inch 
tongues.  The  box  is  surrounded,  at  intervals  of  three  feet  four 
inches,  by  square  frames  of  spruce  timber,  mortised  together  and 
tightened  Avith  bolts  and  wedo-es. 

The  pine  and  spruce  were  fitted  at  the  mills,  so  as  to  go  to- 
gether with  the  least  possible  further  fitting.  As  much  as  250 
feet  in  length  was  assembled  and  spiked  in  a  single  day.  After 
completion  the  whole  was  given  two  coats  of  cheap  paint.  The 
total  cost  of  the  flume  was  a  little  under  $10  per  lineal  foot. 

From  the  further  end  of  the  flume  the  outfall  sewer  (Fig. 
6)  extends  up  to  and  m  front  of  the  storage  reservoir. 


76  MAIN   DRAINAGE   WORKS. 


CHAPTER    IX. 


RESERVOIR    AND    OUTLET. 


Moon  Island  is  distant  about  a  mile  from' the  main  land.  It 
comprises  about  36  acres  of  upland,  surrounded  by  about  145 
acres  of  beaches  and  flats.  The  easterly  end  of  the  island  rises 
to  an  elevation  about  100  feet  above  tide-water.  On  the  west- 
ern or  landward  side  is  another  smaller  area  of  risino;  a:round, 
about  45  feet  high.  Between  these  two  portions  of  high  land 
was  a  valley,  crossing  the  island  from  north  to  south,  whose 
central  portion  was  but  a  few  feet  above  the  level  of  high  water. 
In  this  comparatively  low  land  the  reservoir  is  situated. 

Plates  XXIII.  and  XXIV.  give  views  of  the  reservoir  and 
its  surroundings,  reproduced  from  photographs.  The  former 
was  taken  from  the  high  part  of  the  island  just  east  of  the  res- 
ervoir. It  shows  the  embankment  between  Moon  Island  and 
Squantum,  and  also  the  flume,  parallel  to  and  south  of  the 
embankment.  Near  the  centre  of  the  plate  the  pumping-station 
can  be  dimly  discerned,  although  partly  hidden  by  a  clump  of 
trees  on  Thompson's  Island.  Plate  XXIV.  gives  a  nearer 
view  of  the  reservoir,  looking  eastward.  It  shows  one  basin 
partly  filled  with  sewage. 

The  reservoir,  as  at  present  built,  covers  an  area  of  about 
five  acres.  It  is  expected  that  in  the  future,  when  the  amount  of 
sewage  to  be  stored  shall  have  increased,  it  will  be  necessary  to 
extend  and  enlarge  the  reservoir  to  about  double  its  present 
capacity.  The  portion  already  built  is  so  located  and  arranged 
that  the  contemplated  extension  can  readily  be  made  on  the 
south  side  of  the  present  structure. 

The  site  for  the  reservoir  was  prepared  wholly  b}^  excavating. 
On  the  centre  line  of  the  valley  this  excavation  was  about  ten 
feet  deep,  while  on  the  east  and  west  sides  the  cutting  in  places 
was  forty  feet  deep.  A  drive-way  surrounds  the  reservoir,  and 
the  banks  are  sloped  back  from  it.     The  excavated  material 


Plate  XXIII. 


t35 


Plate  XX I V. 


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m 


RESERVOIR   AND   OUTLET.  77 

was  chiefl}'  hard  clay ;  but  a  bed  of  gravel  and  sand  was  found 
near  the  centre  of  the  valley,  which,  in  places,  went  20  feet 
below  the  reservoir  bottom.  Part  of  the  reservoir,  therefore, 
is  founded  on  clay,  and  another,  smaller  part  on  sand  and  gravel. 

The  earth  was  dug  by  steam  excavators,  and  was  carried 
away  in  cars  by  locomotives.  It  was  used  for  building  the  up- 
per portion  of  the  embankment  between  the  island  and  main 
land.  As  more  earth  was  needed  for  this  purpose  than  could 
be  supplied  from  the  reservoir  excavation  a  further  quantity 
was  l)orrowed  from  the  island  in  such  places  and  to  such  lines 
and  grades  as  partly  to  prepare  the  site  for  the  proposed  future 
extension  of  the  reservoir.  In  all,  about  283,000  cubic  yards 
of  material  were  taken  from  the  island,  and  the  contractor's 
price  for  digging  and  disposing  of  it  averaged  about  59  cents 
per  yard. 

The  retaining- walls  of  the  reservoir  (Fig;  2,  PL  XXVI.)  are 
17.5  feet  high,  and  from  6  feet  10  inches  to  7  feet  10  inches 
thick  at  the  base.  They  are  classed  as  rubble-stone  masonry 
laid  in  mortar,  and  are  built  of  split  and  quarry  stone  mostly 
brought  from  granite  quarries  in  Maine.  On  top  of  the  w^alls 
are  large  coping-stones  with  pointed  surfaces.  The  rubble 
stones  were  laid  in  somewhat  uneven  courses.  The  reservoir  is 
divided  into  four  basins,  of  nearly  equal  area  by  three  division 
walls  (Fig.  3) ,  built  of  the  same  class  of  masonry  as  that 
forming  the  retaining- walls,  liosendale  cement  mortar,  made 
with  one  part  of  cement  to  two  of  sand,  was  use.d  in  building 
rubble-stone  masonry.  The  contractor's  price  for  this  class  of 
masonry  was  $7.47  per  cubic  yard. 

The  floor  of  the  reservoir  consists  of  a  bed  of  concrete,  nine 
inches  thick  (Fig.  6,  Plate  XXV.).  The  lower  five  inches  was 
made  with  Kosendale  cement,  sand,  and  pebbles,  in  the  propor- 
tion of  one,  two,  and  five  parts  of  each  respectively.  In  the 
upper  four  inches  of  concrete,  Portland  cement  was  substituted 
for  Eosendale.  The  floor  of  each  basin  was  shaped  into  alter- 
nate ridges  and  gutters.  The  gutters  are  paved  with  bricks  set 
on  edge. 

Considering  the  distance  of  Moon  Island  from  habitations, 
it  did  not  seem  that  any  just  cause  for  complaint  would  be 


78  MAIN    DRAINAGE    WORKS. 

occasioned  if  the  reservoir  were  left  uncovered,  and,  therefore, 
no  roof  was  built  over  it.  But,  to  provide  for  any  future  contin- 
gency which  might  require  it  to  be  covered,  foundation  blocks 
were  built  into  the  floor,  on  which  piers  to  support  a  roof  can 
hereafter  be  built,  if  needed.  These  foundation  blocks  are 
spaced  20  feet  apart  in  one  direction,  and  30  feet  in  the  other, 
and  consist  of  granite  stones  3  feet  square  and  18  inches  thick. 
They  are  rough-pointed  on  top  and  are  bedded  in  concrete. 
They  cost,  laid,  $7.25  each. 

The  reservoir  was  divided  into  four  distinct  basins,  in  order 
that  one  or  more  of  them  might  be  kept  empty  for  cleaning,  or 
some  similar  purpose,  while  the  others  were  in  use.  Under 
such  conditions,  however,  there  might  be  danger  that  water 
from  a  full  basin  would  find  its  wav  down  throuo;h  the  thin 
sheet  of  concrete  under  it,  and,  passing  below  the  division  wall, 
would  blow  up  the  floor  of  an  adjacent  empty  basin.  This 
would  be  especially  apt  to  occur  where  the  basins  and  walls  are 
underlaid  by  the  pervious  bed  of  gravel  before  referred  to. 

To  diminish  the  liability  to  such  a  catastrophe,  beneath  all 
walls,  not  founded  on  clay,  was  driven  a  solid  wall  of  tongued 
and  grooved  4-inch  sheet-piling.  This  protection  penetrated 
the  gravel  stratum  and  entered  the  clay  below  it.  As  an  addi- 
tional precaution  at  such  places  a  line  of  10-inch  drain-pipe 
was  laid  just  below  the  floor  on  each  side  of  the  division  wall. 
These  drains  were  connected  with  others  surrounding  the 
reservoir  outride  of  the  retaining-walls.  The  drains  within 
the  reservoir  also  have  10-inch  safety-valves  opening  into  the 
basins.  The  drain-pipes  were  laid  with  open  joints,  and  were 
surrounded,  below  the  concrete,  with  dry-laid  ballast  and  peb- 
bles. Water  accumulating  beneath  the  floor  of  any  basin  has 
free  access  to  the  drain  under  that  basin.  Should  any  water 
find  its  way  under  a  division  wall  it  is  immediately  intercepted 
by  the  line  of  pipe  just  beyond  the  wall.  Should  a  drain  under 
an  empty  basin  become  gorged  for  any  reason,  the  water  is 
discharged  into  the  basin,  through  the  safety-valve,  before  sufii- 
cient  head  has  accumulated  to  endanger  the  concrete. 

The  northerly  100  feet  of  each  division  wall,  being  the  end 
nearest  to  the  discharge  sewers,  is  made  hollow,  and  1.75  feet 


Plate  XXV. 


EESERVOIE    AND    OUTLET.  79 

lower  than  the  rest  of  the  reservoir  walls  (Plate  XXV.,  Fig. 
4).  Long  chambers  are  thus  formed,  open  on  top,  but  other- 
wise enclosed  within  the  walls.  These  chambers  connect  di- 
rectly w4th  the  discharge  sewers,  and  through  them  with  the 
harbor.  These  portions  of  the  division  walls  serve  as  waste 
weirs,  by  which  the  sewage  in  the  basins  can  overflow,  if,  owing 
to  negligence  on  the  part  of  the  employees,  the  gates  which 
empty  any  basin  should  not  be  opened  before  the  basin  be- 
comes too  full. 

The  arrangements  by  which  the  sewage  is  turned  from  the 
outfall  sewer  into  the  reservoir  and  is  again  permitted  to  empty, 
throuo'h  the  discharo-e  sewers,  into  the  harbor,  will  be  under- 
stood  from  an  examination  of  Fig.  1,  Plate  XXV.,  which  is  a 
transverse  section  of  said  sewers.  The  upper  sewer  in  the  fig- 
ure is  a  continuation  of  the  outfall  sewer,  and  extends  along  the 
whole  front  of  the  reservoir.  Immediately  below  it  are  the 
discharge  sewers,  which  also  extend  along  the  front  of  the 
reservoir,  and,  also,  about  600  feet  beyond  it  out  into  the  sea. 

In  the  side  of  the  outfall  sewer  are  20  3  X  4  feet,  cut-stone 
gate  openings.  Only  eight  of  these  are  at  present  provided  with 
gates,  the  others  being  bricked  up  until  an  increased  amount  of 
sewage  and  an  extension  of  the  reservoir  shall  require  their  use. 
In  the  side  of  the  discharge  sewer  nearest  the  reservoir  are  also 
20  gate  openings,  of  which  12  are  provided  with  gates.  The 
two  discharge  sewers  are  connected  directly  by  11  large  trans- 
verse passages.  The  amount  of  masonry  contained  in  and 
surrounding  the  sewers  equals  that  contained  in  all  of  the  res- 
ervoir walls. 

Between  the  sewers  and  the  reservoirs  is  what  is  called  the 
six-foot  gallery.  This  serves  as  a  protection  for  the  gates 
against  frost  and  as  a  foundation  for  a  gate-house  above.  The 
hollow  division  walls  between  the  basins  extend  across  the  gal- 
lery and  divide  it  into  four  sections,  corresponding  with  the 
four  basins  of  the  reservoir.  Brick  brace- walls,  about  10.5 
feet  apart,  are  thrown  across  from  the  sewers  to  the  reservoir 
■wall. 

The  20  gates,  with  their  frames  and  seats,  are  made  of  cast- 
iron.     The  frames  were  cast  in  one  piece  and  closely  fitted  to 


80  MAIN   DRAINAGE    WORKS. 

the  openings  prepared  in  the  masonry.  They  are  secured  to  the 
stone  by  |-inch  anchor-bolts,  let  in  4|^  inches  and  fastened  with 
brimstone.  The  seat  of  each  gate  is  a  separate  piece  of  cast- 
iron,  planed  |-inch  thick,  fastened  to  its  frame  with  screw 
rivets,  and  scraped  true  and  straight.  Fastened  to  each  side  of 
the  frame  is  a  guide,  which  holds  the  valve  in  its  proper  posi- 
tion while  moving.  The  face  of  the  valve  is  planed  and  scraped 
to  fit  the  facing  of  the  frames,  so  that  there  shall  be  no  leak- 
age. The  valve  is  pressed  tight  to  its  seat  by  means  of  adjust- 
able gibs,  which  bear  against  inclined  planes,  cast  on  the 
guides. 

The  gates  are  moved  by  lifting-rods  and  screws,  connected 
with  suitable  brackets,  gearing,  and  clutches,  above  the  floor 
of  the  gate-house  (Plate  XXV.  Fig.  2).  A  main  line  of  shaft- 
ing, from  2^  to  3^  inches  in  diameter,  extends  the  whole  length 
of  the  gate-house,  or  about  575  feet.  The  clutches  for  each 
gate  are  thrown  in  and  out  by  a  hand  lever,  and  also  by  the 
gate  itself  when  it  reaches  either  end  of  its  course.  The  20 
gates,  with  all  their  appurtenances  and  the  gearing  and  shafting 
for  operating  them,  cost,  in  place,  about  $12,000. 

To  furnish  power  both  a  steam-engine  and  a  turbine  wheel 
are  provided.  The  latter,  which  is  most  commonly  used,  is 
21  inches  in  diameter,  and  is  placed  in  a  well  near  the  north- 
easterly corner  of  the  reservoir.  It  takes  water  either  from 
the  reservoir  or  from  the  outfall  sewer,  and  drains  into  the  dis- 
charge sewers.  Under  ordinary  circumstances  it  furnishes 
without  expense  ample  power  for  moving  the  gates,  running 
pumps,  and  other  necessary  operations,  and  requires  no  atten- 
tion beyond  opening  and  shutting  the  gates  leading  to  it. 

The  engine,  which  is  seldom  used,  is  of  30  horse-power.  To 
furnish  steam  for  it  and  also  for  heating  in  wintei",  there  are  two 
upright  tubular  boilers.  The  machinery  and  gates  are  pro- 
tected by  suitable  brick  buildings,  designed  and  built  by  the 
engineers.  The  principal  one  of  these,  called  the  Long  Gate- 
House,  extends  for  575  feet  along  the  front  of  the  reservoir. 
Connecting  with  it,  at  the  north-easterly  corner  of  the  reservoir, 
is  another  larger  building,  containing  engine,  boiler,  and  coal 
rooms.     A  chimney,  40  feet  high,  is  also  built. 


SHOW/NG 
P/ER  AND  COrrEH  DAM. 


Plate  XXVI. 


C/TY  or  BOSTON  MA/N  DRA/NA G^. 

D/SCHAHQi:  S£IV£/fS  BEYOND  RESEBVOm 


RETAINING  WALL   OF  BESERVOIR 
GENERAL   SECTION. 


DIVISION  WALL 
ON  PER  VIOUS  MA  TERIAL . 


HOLLOW  DIVISION  WALL 
SECTION  M.  N.  PL.  XXV. 


RESERVOIR    AND    OUTLET.  81 

The  sewage  flows  throus;!!  the  spates  in  the  outfall  sewer 
into  the  six-feet  gallery,  whence  it  passes  through  openings  in 
the  reservoir  wall  into  the  reservoir.  There  it  accumulates 
during  the  latter  part  of  ebb-tide  and  the  whole  of  the  flood- 
tide.  Shortly  after  the  turn  of  the  tide  the  lower  gates  are 
opened,  and  the  sewage  flows  from  the  reservoir,  through  the 
gallery,  into  the  discharge  sewers,  which  conduct  it  to  the  out- 
let. 

That  portion  of  the  discharge  sewers  beyond  the  reservoir 
was  called  the  Outlet-Sewer  Section,  and  was  built  under  a 
separate  contract.  There  are  two  sewers  of  brick  and  concrete 
masonry  (Fig.  1,  Plate  XXVI.),  each  10  feet  10  inches  high, 
by  12  feet  wide  inside.  They  extend  from  the  reservoir  about 
600  feet  out  into  the  sea,  where  there  is  five  feet  depth  of  water 
at  low  tide.  The  bottoms  of  the  sewers  are  1.5  feet  above  the 
elevation  of  low  water.  The  arches,  12  inches  thick,  were  laid 
with  Rosendale  cement  mortar,  and  the  inverts  and  sides  with 
Portland  cement  mortar.  In  the  top  of  each  sewer  are  built 
three  large  vent-holes,  to  relieve  the  arch  from  any  pressure  of 
air  due  to  a  succession  of  waves  entering  the  sewers. 

The  immediate  outlet  consists  of  a  cut  granite  pier-head  laid 
in  mortar.  In  this  are  chambers  containing  grooves  for  gates 
and  stop-planks.  The  stones  forming  the  pier-head  are  quite 
large,  in  order  to  withstand  waves  and  ice.  Several  of  them 
weighed  about  eight  tons  each.  Most  of  the  horizontal  joints 
are  do  welled,  and  the  vertical  joints  of  the  coping-stones  are 
secured  by  gun-metal  cramps. 

The  sewers  are  covered  by  an  earth  embankment,  with  its  side 
slopes  protected  by  ballast  and  rip-rap.  This  embankment 
constitutes  a  pier  extending  into  the  harbor,  and  its  top  is 
ballasted  and  surfaced  for  a  roadway.  Xear  the  end  of  the  pier 
is  a  strong  wharf,  about  40  feet  square,  supported  by  oak  piles. 
This  is  used  for  landing  coal  and  other  supplies. 

To  facilitate  construction  on  this  section  the  site  of  the  work 
was  enclosed  by  building  about  1,100  feet  of  cofl'er-dam  around 
it.  The  dam  consisted  of  two  rows  of  spruce  piles,  ten  feet  apart, 
the  piles  in  each  row  being  spaced  six  feet  on  centres.  Inside 
the  piles  were  rows  of  4-inch  tongued  and  grooved  sheet-piling. 


82  MAIN    DRAINAGE    AVORKS. 

The  dam  was  tied  across  with  iron  bolts  and  was  filled  with 
earth.  When  pumped  out  it  proved  to  be  very  tight,  and 
enabled  the  work  inside  it  to  proceed  without  interruption.  After 
the  sewers  were  built  and  covered,  the  dam  was  cut  down  below 
the  surface  of  the  embankment  slopes.  The  total  cost  of  this 
outlet  section  was  $96,250. 

The  top  of  the  I'eservoir  floor  is  about  one  foot  below  the  eleva- 
tion of  high  water.  The  paved  gutters  are  a  little  lower,  and  in- 
cline nearly  a  foot  from  the  back  of  the  reservoir  to  its  front.  This 
insures  there  being  a  good  current  in  them  when  the  reservoirs 
are  nearly  emptied,  so  that  the  light  deposit  of  sludge  which  has 
been  precipitated  upon  the  bottom  of  the  reservoir  is  mostly 
washed  into  the  discharge-sewers. 

To  assist  in  cleansing  the  basins,  a  system  of  pipes  and 
hydrants  furnishing  salt  water  under  pressure  is  provided.  The 
water  is  drawn  from  the  sea  to  a  pump  in  the  engine-house, 
which  forces  it  about  the  reservoir.  A  4-inch  pipe,  with 
double  hydrants,  about  75  feet  apart,  is  laid  through  the  middle 
of  each  basin.  A  line  of  hose  can  be  connected  with  any 
hydrant,  and  a  fire-stream  directed  against  any  part  of  the  floor 
or  side  walls.  The  pump  can  also  be  used  to  pump  sewage  with 
which  to  irrigate  the  banks  and  grounds  surrounding  the  reser- 
voir. 

To  obtain  fresh  water  for  domestic  purposes  and  for  the 
boilers,  the  high  portion  of  the  island  has  been  encircled  with 
ditches,  which  collect  rain-water  and  conduct  it  to  a  cistern  hold- 
ing 75,000  gallons. 

Within  the  gate-house  is  provided  an  automatic  recording 
gauge,  moved  by  clock-work  and  connected  with  floats  in  the 
sewers.  The  records  traced  by  this  machine  furnish  a  per- 
fect check  on  the  vigilance  of  the  employees.  Each  day's  record 
shows,  by  inspection,  the  hours  at  which  the  gates  were  opened 
and  closed  and  the  height  of  tide. 

The  total  expenditure  by  the  city  on  account  of  Main  Drain- 
age Works,  from  the  beginning  of  the  preliminary  survey,  1876, 
to  the  present  time,  is  about  $5,213,000. 


DETAILS   OF   ENGINEERING   AND    CONSTRUCTION.  83 

CHAPTER   X. 

DETAILS    OF    ENGINEERING    AND    CONSTRUCTION. 

About  one-half  of  the  work  required  to  complete  the  Main 
Drainage  System  was  done  by  contract,  and  the  rest  by  day's 
labor,  under  superintendents  appointed  by  the  city.  The  general 
rule  by  which  it  was  decided-  whether  any  given  section  of  work 
should  be  built  by  contract,  or  not,  was  this  :  if  the  work  was  of 
such  a  nature  that  its  extent  and  character  could  be  determined 
in  advance,  so  that  full  and  explicit  specifications  for  it  could  be 
drawn,  it  Avas  let  out  by  contract  to  the  lowest  responsible 
bidder.  If,  on  the  other  hand,  all  of  the  conditions  liable  to 
affect  the  work  could  not  be  ascertained,  so  that  it  was  antici- 
pated that  modifications  in  the  proposed  methods  of  construction 
might  prove  necessary  or  desirable,  the  work  was  done  by  day's 
labor. 

Thus,  wherever  in  suburban  or  thinly  populated  districts  the 
character  of  the  earth  to  be  excavated  was  supposed  to  be  of 
uniform  quality,  most  of  the  sewers  there  located  were  built  by 
contract.  Those  located  in  crowded  thoroughfares,  where  it 
was  necessary  to  interfere  as  little  as  possible  with  the  use  of 
the  street,  and  those  in  places  where  there  was  liability  of  en- 
countering deep  beds  of  mud,  old  walls,  wharves,  and  other  ob- 
stacles, were  built  by  day's  labor. 

There  was  little  difference  in  the  quality  of  the  work  obtained 
by  these  different  methods  of  construction.  The  contract  work 
was  built  under  more  favorable  conditions,  and  as  a  whole  is 
somewhat  superior  to  the  other.  It  also,  as  a  rule,  cost  much 
less.  Several  reasons  can  be  given  for  this  fact.  The  physical 
conditions  were  generally  more  favorable.  Low  prices  were 
obtained  through  competitive  bids.  Most  of  the  contractors 
made  no  profit ;  some  even  lost  money.  The  contract  work 
was  largely  done  during  the  first  few  years  of  construction, 
when  all  prices  were  lower ;  while  the  bulk  of  the  work 
done  by  day's  labor  was  built  later,  when  prices  for  labor  and 


84  MAIN    DEATNAGE    WORKS. 

materials  had  risen.  The  wages  paid  city  laborers  were  fixed 
by  the  City  Council,  and  were  always  higher  than  the  market 
rates.  At  times  the  city  superintendents  were  not  untrammelled 
m  respect  to  hiring  and  discharging  their  employees. 

Sixteen  sections  of  sewer  were  let  by  contract.  In  two 
cases  the  contractors  failed,  and  the  sections  were  relet.  In 
four  other  cases  the  contractors  abandoned  their  work,  which 
was  completed  by  the  city,  by  day's  labor.  In  connection  with 
the  Main  Drainage  System  about  50  more  contracts  were  made 
for  materials  and  machinery,  and  for  construction  and  work 
other  than  sewer  building.  These  contracts  were  drawn  by  the 
engineers. 

In  preparmg  a  contract  for  building  a  sewer  the  object  kept 
in  view  was  to  describe  only  the  general  character  of  the  work, 
and  to  leave  for  further  decisions,  as  construction  progressed, 
the  exact  shape,  methods  of  construction,  and  amounts  and 
kinds  of  materials  to  be  used.  That  this  might  be  done  with- 
out unfairness  to  the  contractor  the  precise  character  (but  not 
the  amount)  of  every  kind  of  work  and  material,  which  miglit 
be  called  for,  was  specified,  and  a  price  was  agreed  on  for  each. 
Should  anything  not  specified  be  called  for,  the  contractor 
agreed  to  furnish  it  at  its  actual  cost  to  him,  plus  15  per  cent, 
of  said  cost. 

This  is  a  convenient  form  of  contract,  because  it  permits  the 
engineer  to  modify  his  methods  of  construction  whenever  ex- 
perience shows  that  a  change  is  desirable.  One  kind  of  mate- 
rial can  be  substituted  for  another;  cradles,  side  walls,  and 
piling  can  be  added  or  discarded.  Rather  more  opportunities 
for  contention  are  afforded  by  this  form  of  contract  than  by  a 
simpler  one ;  but,  on  the  whole,  it  was  considered  the  best  for 
our  purposes. 

Contract  work  was  carefully  watched,  an  inspector  being 
continually  on  the  ground.  Great  care  was  taken  to  select 
suitable  men  for  such  positions.  They  were  all  experienced 
masons,  and  were  paid  $4.00  or  more  a  day. 

A  daily  force  account  was  always  kept,  both  of  work  done 
by  the  city  and  that  built  by  contract.  This  recorded  the  number 
of  hours'  labor  of  every  class  and  the  amount  of  material  which 


DETAILS   OF   ENGINEERING   AND   CONSTRUCTION.  85 

entered  into  each  part  of  the  work,  so  that  its  cost  could  be 
ascertained.  On  contract  work  this  record  proved  very  useful, 
because  it  furnished  conclusive  evidence  in  any  case  of  disa- 
greement as  to  quantities  or  cost. 

All  materials  were  carefully  inspected  for  quality.  Especial 
care  was  exercised  in  inspecting  bricks  and  cement.  About 
50,000,000  of  the  former  and"l80,000  casks  of  the  latter 
material  were  used  in  building  the  works.  It  was  required 
that  the  bricks  should  be  uniform  in  size,  regular  in  shape, 
tough,  and  burned  very  hard  entirely  through.  Bricks  with 
black  ends  were  not  excluded  if  otherwise  suitable.  No  machine- 
made  bricks  were  accepted,  as  they  were  usually  found  to  have 
a  laminated  structure.  A  moderate  proportion  of  bats  was 
allowed,  but  only  in  the  outer  ring  of  the  covering  arch.  From 
the  accepted  bricks  the  most  regular  were  culled  out  for  inside 
work.  Bricks  from  diflferent  localities  varied  considerably  in 
size,  and  this  fact,  so  often  disregarded,  was  taken  into  account 
in  making  purchases  for  the  city.  For  instance,  1,175  Bangor 
bricks  were  required  to  build  as  much  masonry  as  could  be 
built  with  1,000  Somerville  bricks. 

A  requirement  that  no  bricks  should  be  used  which  would 
absorb  more  than  16  per  cent.,  in  volume,  of  water,  although 
not  always  enforced,  was  occasionally  found  useful,  because  it 
permitted  the  rejection  of  bricks  made  of  light,  sandy  stock, 
which  were,  however,  perfectly  hard  and  shapely.  The  fol- 
lowing was  the  method  employed  in  testing  for  porosity.  The 
brick  to  be  tested  was  first  dried  thoroughly  by  artificial  heat, 
and  then  weighed.  Next  it  was  put  in  a  pan  containing  one- 
half  inch  of  water  and  allowed  to  soak  for  24  hours,  the  pan 
being  gradually  filled,  by  adding  water  from  time  to  time  until 
the  brick  was  covered.  When  thoroughly  soaked  it  was  again 
weighed,  both  in  water  and  in  air.  The  difiference  between 
the  weights  dry  and  soaked,  in  air,  was  the  weight  of  water 
absorbed,  and  the  difierence  between  the  weights  of  the  soaked 
brick,  in  air  and  in  water,  was  the  loss  of  weight  in  water, 
i.e.,    the  weight   of  a    bulk    of  water   equal   to    that    of  the 

1     •    1         J.1  The  weight  of  water  alDsorbed  j_v  ,•  •  i 

brick  ;  then    The  iosb  of  weight  m  water    was  the  proportion,  m  volume, 
of  water  absorbed  by  the  brick. 


86  MAIN   DRAINAGE   WORKS. 

Natural  "  E,osendale  "  cement  was  chiefly  used  on  the  work, 
but  about  26,000  barrels  of  Portland  cement  and  a  little  Roman 
cement  were  also  used.  Portland  cement  mortar  was  often 
used  in  building  the  inverts  of  sewers  and,  in  general,  where 
there  was  liability  to  abrasion  or  where  especial  strength  was 
needed.  It  was  often  mixed  with  Rosendale  cement  in  order  to 
make  a  somewhat  stronger  mortar.  Very  quick-setting  Roman 
cement  was  used  for  stopping  leaks,  and  was  also  mixed  with 
other  cements  for  wet  work,  because  it  would  set  at  once  and 
keep  the  mortar  from  being  washed  down  before  the  stronger 
cements  had  hardened. 

In  Appendix  A  is  given  a  full  account  of  the  methods  em- 
ployed for  testing  cement,  and  also  the  results  derived  from 
the  tests  made  for  experimental  purposes.  One  advantage 
resulting  from  the  careful  and  systematic  testing  was  that  manu- 
facturers and  dealers  were  themselves  careful  to  offer  or  send 
no  cement  but  that  which  they  felt  confident  would  be  accepted. 
During  the  first  year  or  two  much  of  the  cement  offered  was 
rejected,  but  later  very  little  of  it  proved  unacceptable.  In 
makino;  contracts  for  cement  a  standard  of  streno;th  and  fine- 
ness  was  seldom  given.  It  was  simply  stipulated  that  the 
cement  should  be,  in  every  respect,  satisfactory  to  the  engineer, 
and,  if  not  satisfactory,  should  be  rejected. 

In  one  contract,  how^ever,  for  5,000  barrels  of  Portland  ce- 
ment, a  certain  fineness  and  strength  were  required.  As  some 
of  the  specifications  of  this  contract  are  believed  to  be  novel 
and  practically  useful,  they  are  here  cited  :  — ; 

Fineness.  The  cement  to  be  very  fine  ground,  so  that  not  over  fifteen 
(15)  per  cent,  of  it  will  be  retained  by  a  certain  sieve  deposited  in  the  ofiice 
of  the  City  Engineer  of  Boston,  said  sieve  having  14,400  meshes  to  the 
square  inch. 

Strength.  The  cement,  when  gauged  with  three  pai'ts  by  measure  of 
sand,  to  one  part  of  cement ;  formed  into  briquettes  having  a  breaking  area 
of  '2\  square  inches ;  kept  28  days  in  water  and  broken  from  the  water,  to 
have  a  tensile  strength  of  150  lbs.  per  square  inch. 

Price.  We  agree  to  receive  as  full  payment  for  the  satisfactory  delivery 
of  said  cement,  subject  to  its  fulfilment  of  the  foregoing  requirements,  as 
determined  by  the  City  Engineer  of  Boston,  the  smn  of  three  dollars  ($3.00) 
per  cask  delivered  and  accepted. 

We  further  agree,  that,  shall  the  cement,  or  any  portion  thereof,  fail  to 


■     DETAILS    OF   ENGINEERING   AND   CONSTEUCTION.  8< 

fulfil  the  above-mentioned  requirement  as  to  fineness,  but  shall  nevertheless 
be  accepted  by  the  city,  we  will  receive  as  full  payment  for  said  cement,  or 
said  portion  thereof,  a  sum  to  be  determined  by  the  City  Engineer,  by 
deducting  from  the  full  price,  of  three  dollars  ($3.00)  per  cask,  the  sum 
of  two  cents  ($0.02)  per  cask  for  each  per  cent,  greater  than  15  per  cent, 
that  is  retained  by  the  sieve  before  mentioned. 

Contractors  were  required  to  use  only  clean,  sharp,  coarse 
sand  for  making  mortar.  On  city  work,  if  clean  sand  was  not 
conveniently  accessible,  a  moderately  dusty  or  dirty  sand  was 
considered  almost  as  good,  and  quite  good  enough.  So,  also, 
in  making  concrete,  contractors  were  obliged  to  use  screened 
sand  and  stone  ;  but  a  city  superintendent  might  mix  his  cement 
directly  with  the  gravel  dug  from  the  bank,  if  it  was  more  con- 
venient and  cheaper  to  do  so.  Comparative  tests  of  concrete 
made  by  these  diJfferent  methods  failed  to  distinguish  any  supe- 
riority in  one  over  the  other. 

The  city  sewers  were  so  low  that  the  intercepting  sewers, 
which  had  to  be  lower  still,  required  unusually  deep  trenches. 
The  average  depth  of  cut  for  the  whole  system  was  more  than 
21  feet.  The  bottom  of  these  trenches  was  generally  several 
feet  below  the  elevation  of  low  tide.  As  the  new  sewers  fol- 
lowed the  margins  of  the  city  near  the  sea,  tide-water  frequently 
found  access  to  the  trenches,  so  that  construction  could  only 
proceed  during  a  few  hours  at  about  the  time  of  low  tide,  when 
the  leakage  of  water  could  be  controlled.  Sometimes  the  trench 
could  not  be  kept  entirely  free  from  water.  Many  of  the  streets 
traversed  by  the  sewers  were  underlaid  by  beds  of  mud.  Gen- 
erally the  mud  was  not  so  deep  but  that  an  un3delding  founda- 
tion could  be  secured  by  driving  piles  through  the  mud  down 
into  the  hard  ground  beneath.  Sometimes,  however,  the  mud 
was  so  deep  that  hard  bottom  could  not  be  reached  by  piling. 

It  was  under  such  conditions  that  the  use  of  wood  to  form 
the  whole,  or  the  lower  part,  of  the  sewer  was  resorted  to. 
Wood  was  no  cheaper  in  itself  than  masonry ;  but  a  wooden 
sewer  could  be  built  very  much  more  rapidly  than  a  brick  one, 
and  could  be  built  by  unskilled  laborers.  Also,  a  wooden 
invert  could  be  fastened  in  place,  if  necessary,  under  a  foot  or 
two  of  water.     Moreover,  a  wooden  sewer,  fastened  by  spikes 


0«  MAESr   DRAINAGE   WORKS. 

and  oak  treenails,  possessed  considerable  elasticity,  and  could 
settle  slightly  in  places,  or  assume  an  undulating  form,  without 
breaking. 

Therefore,  under  conditions  such  as  those  just  mentioned, 
the  use  of  wood  to  form  the  shell  of  a  sewer  was  often  resorted 
to.  There  were  disadvantages  attending  this  mode  of  con- 
struction. The  elasticity  which  permitted  the  sewer  to  bend 
longitudinally  without  breaking,  also  made  it  tend  to  yield  trans- 
versely, sinking  at  the  crown  and  bulging  at  the  sides,  when- 
ever the  earth  outside  was  at  all  compressible.  It  was  not  easy 
to  prevent  the  wooden  shell  from  leaking  badly,  especially  at 
the  end  joints.  All  wooden  sewers  had  to  be  lined  with  brick- 
work, or  concrete,  to  make  them  smooth  and  tight ;  but  putting 
such  lining  inside  of  a  leaky  sewer  is  a  somewhat  tedious  and 
difficult  operation. 

The  tops  of  most  of  the  intercepting  sewers  are  several  feet 
below  the  level  at  which  ground  water  stands  in  the  earth  about 
them.  Great  pains  were  taken  to  insure  every  joint  being 
thoroughly  filled  with  mortar,  and  the  arches  were  always  plas- 
tered outside  with  a  half-inch  coating  of  cement  mortar.  By 
such  means  the  greater  part  of  the  system  was  made  perfectly 
tight  and  dry.  In  places,  however,  especially  where  there  were 
slight  settlements  and  cracks,  a  considerable  amount  of  leakage 
occurred.  All  leaky  joints  were  calked  as  well  as  possible. 
Various  materials  were  used  for  this  purpose.  Among  them 
were  neat  cement ;  cement  mixed  with  grease  or  with  clay  ; 
oakum  ;  dry  pine  wedges,  and  sheet  lead.  Bj^  one  or  several  of 
these  methods  the  leakage  could  either  be  entirely  stopped  or 
reduced  to  an  insignificant  amount. 

A  considerable  item  in  the  total  cost  of  building  the  inter- 
cepting system  was  the  expense  incurred  in  repairs  to  street 
surfaces  and  paving,  over  the  sewers.  The  trenches  were  so 
large  and  deep  that  the  backfilling,  often  of  a  peaty  consist- 
ency, could  not  be  sufficiently  compacted  by  ramming  or  pud- 
dlino-  but  continued  to  settle  for  a  vear  or  more  after  the 
sewer  was  built.  As  it  was  necessary  to  keep  the  surface  in  a 
safe  and  reasonably  smooth  condition  the  portion  over  the 
trench  was  sometimes  repaved  three,  or  even  more,  times  before 


DETAILS    OF    ENGINEERING   AND    CONSTRUCTION.  89 

it  would  remain  permanently  in  place.  Where  the  earth  un- 
derlying the  street  was  of  a  peaty  nature,  it  would  be  rendered 
spongy  and  compressible  by  its  water  draining  out  into  the  open 
trench  during  construction.  Then  the  whole  street  surface, 
including  sidewalks  and  sometimes  even  adjacent  yards,  would 
settle  out  of  shape  and  need  repairing. 

Another  source  of  expense  and  trouble  was  the  breaking  of 
house-drains  where  they  passed  across  the  sewer  trench,  due  to 
the  settlement  of  the  backfilling.  The  intercepting  sew^ers 
were  frequently,  indeed  generally,  built  in  streets  which 
already  contained  a  common  sewer.  The  house-drains  from 
one  side  of  the  street  crossed  the  trench  of  the  hitercepting 
sewer.  These  drains  were  maintained,  or  replaced,  as  securely 
as  possible,  but  many  of  them  were  afterwards  broken. 
These  were  generally  found  to  be  sheared  off  on  the  line  of  the 
sides  of  the  excavation,  and  the  portion  within  the  trench  sunk 
bodily,  half  a  foot  or  so,  below  the  rest. 

As  a  rule  the  streets  in  which  sewers  were  built  were  kept 
open  for  traffic.  When  the  trench  was  in  the  middle  of  the 
street,  passage-ways  for  vehicles  were  maintained  on  both  sides 
of  it,  even  when  the  width  between  sidewalk  curbs  was  only  26 
feet.  This  was  accomplished  by  the  use  of  an  apparatus  for  ex- 
cavating and  backfilling,  invented  by  the  superintendent,  Mr.  H. 
A.  Carson,  and  afterwards  patented  by  him.  Various  merits 
are  claimed  for  it,  but  the  chief  advantage  in  its  use  at  Boston 
was,  that  by  it  sewers  could  be  built  with  very  little  encroach- 
ment on  the  surface  of  the  street.  Views  of  the  apparatus  are 
given  on  Plate  XXVII.  Although  a  patented  article,  a  brief 
description  of  it  seems  proper,  since  it  was  used  in  building 
more  than  one-half  of  the  intercepting  sewers. 

In  its  general  features  the  apparatus  consisted  of  a  light 
frame  structure,  extending  longitudinally  over  the  sewer  trench 
from  a  point  in  advance  of  where  excavation  had  begun,  to 
another  behind  where  the  trench  was  completely  backfilled. 
All  operations,  therefore,  were  carried  on  beneath  the  machine. 
Excavation  proceeded  under  the  forward  portion  of  the 
frame,  the  sewer  was  built  under  the  central  portion,  and 
backfilling  progressed  near  the  rear.     A  double-drum  hoisting 


00  MAIN    DRAINAGE    WORKS. 

engine  was  carried  on  a  platform  at  the  front  end  of  the  frame. 
From  the  top  of  the  frame  were  suspended  iron  tracks,  on  which 
were  travellers,  moved  backwards  and  forwards  by  wire  ropes 
leading  to  the  engine.  A  number  of  tubs,  loaded  by  the  dig- 
gers in  front,  were  hoisted  simultaneously  by  the  engine,  and 
run  back  to  be  dumped  over  the  completed  sewer.  They  were 
then  returned  and  lowered  to  the  points  whence  they  had  been 
taken,  by  which  time  a  second  set  of  tubs  had  been  filled  ready 
for  hoistino;. 

Any  surplus  earth  was  dumped  through  a  hopper  into  carts 
which  were  backed  mider  the  machine.  When  it  was  neces- 
sary to  furnish  a  passage  across  the  work  the  trench  was 
bridged,  and  the  frame  trussed.  When  one  section  of  excava- 
tion was  completed,  the  whole  apparatus,  which  rested  on 
wheels,  was  pulled  forward  30  or  more  feet  by  its  own  engine. 
The  average  total  length  of  one  apparatus  was  200  feet,  and  its 
total  weight  about  10  tons. 

Sewer  building,  done  by  the  city,  was  frequently  carried  on 
through  the  winter  months.  Contractors,  on  the  other  hand, 
were  not  allowed  to  lay  masonry  between  November  15  and 
April  15.  The  temperature  at  the  bottom  of  a  deep  trench  was 
always  considerably  higher  than  that  at  the  surface  of  the  ground  ; 
so  that  it  was  only  when  the  mercury  was  at  ten  or  more  de- 
grees (F.)  below  the  freezing-point  that  work  was  suspended. 
Much  extra  precautionary  work  was  needed.  Bricks  were 
steamed  in  a  close  box  before  using ;  sand  and  water  were 
warmed,  and  completed  work  was  protected  by  coverings  of 
straw  or  sea-weed.  Winter  work  was  not  economical,  and  was 
resorted  to  chiefly  for  the  purpose  of  employing  laborers,  who 
otherwise  might  have  been  idle. 

Experience  is  probably  a  better  guide  to  designing  stable 
sewers  than  are  theories  concerning  lines  of  pressures  and  geo- 
static  arches.  The  physical  conditions  which  determine  the 
direction  and  amount  of  the  earth  pressures  are  seldom  the  same 
in  the  case  of  any  two  sewers.  They  differ  at  different  points 
about  the  same  sewer,  and  often  are  not  alike  on  both  sides  of 
one  sewer.  The  best  that  can  be  done  is  to  judge  as  well  as 
possible  of  the  character  of  the  ground  to  be  penetrated,  and 


Plate   XXVII 


TRENCH      MACHINE 


MT.  VERNON   ST.    1883. 


Fig.  I 

CITY  OF  BOSTON 
MAIN     DRAINAGE 


DIAGRAM    machine: 


STOP      PLANKS 

3,        •^■'^•3 


i 


Fig.  2 


Fig.  4- 


DETAILS    OF   ENGINEERING   AND   CONSTEUCTION.  91 

befjin  to  build  such  a  sewer  as  has  proved  stable  under  similar 
conditions.  The  sewer  should  then  be  examined  carefully, 
during  and  after  loading,  for  signs  of  weakness. 

In  the  case  of  the  main  drainage  sewers  such  examinations 
were  made  graphically,  by  taking  diagrams  of  their  inside 
shape.  These  diagrams  were  taken  by  the  aid  of  a  machine 
shown  on  Plate  XXVII.  It  consisted  of  a  light  frame,  which 
could  be  so  fixed  against  the  masonry  that  its  centre  should 
be  in  the  axis  of  the  sewer.  A  movable  arm  was  then  rotated 
radially  from  the  centre,  with  its  outer  end  bearing  lightly 
against  the  inside  perimeter  of  the  sewer.  At  the  centre  of  the 
machine  was  a  disk,  on  which  was  placed  a  sheet  of  paper.  A 
pencil  point,  attached  to  the  rotating  arm,  traced  upon  the 
paper  a  diagram,  showing  the  shape  of  the  sewer  and  its  varia- 
tion, if  any,  from  the  established  form. 

The  shape  and  amount  of  any  distortion  suggested  the  cause 
which  produced  it,  and  the  remedy  to  be  applied.  The  most 
common  causes  were  too  early  removal  of  centres ;  too  rapid 
or  unequal  loading  ;  the  use  of  improper  material  for  backfilling 
about  the  sewer  ;  insufficient  rammino;  of  backfillina:  ao-ainst  the 
haunches  ;  withdrawing  sheet  planks  after  backfilling  ;  inherent 
weakness  in  the  design  of  the  sewer.  Such  errors  could  be 
corrected  and  the  design  of  the  structure  could  be  modified 
until  the  diagrams  taken  from  the  sewer  were  found  to  corre- 
spond with  its  proper  shape. 

The  Main  Drainage  System  is  so  arranged  that  any  principal 
portion  of  it  cafi  be  isolated  and  emptied  for  inspection  and  re- 
pair. Any  intercepting  sewer  can  be  thus  isolated  by  closing 
the  penstock  gate  at  its  lower  end,  and  also  the  inlet  valves 
connecting  it  with  the  common  sewers,  the  latter  then  discharg- 
ing at  their  old  outlets.  By  closing  the  gates  at  the  ends  of  all 
intercepting  sewers  the  main  sewer  can  be  emptied.  Wher- 
ever an  opportunity  for  isolating  a  small  portion  of  the  works 
might  prove  desirable,  but  the  use  of  iron  gates  for  such  pur- 
pose would  have  entailed  unwarranted  expense,  as  a  cheaper 
substitute,  grooves  of  iron  or  stone  were  built  into  the  masonry 
for  stop-planks.  Such  grooves  for  stop-planks  were  always 
built  above  any  iron  gates,  to  afford  a  means  of  access  in  case 


92  MAIN  DRAINAGE    WORKS. 

of  needed  repairs.  Where  slight  leakage  could  be  afforded,  a 
sino-le  pair  of  grooves  were  considered  sufficient.  Where  a 
tio-ht  dam  was  desirable,  a  double  set  of  grooves  was  provided, 
so  that  a  double  set  of  stop-planks,  with  an  inside  packing  of 
clay,  could  be  used.  Some  hundreds  of  stop-planks,  of  differ- 
ent lengths,  are  kept  in  readiness.  Their  form  is  shown  on 
Plate  XXVII.  They  are  made  of  hard-pine  planks,  from  three 
to  five  inches  thick,  jjlaned  and  oiled. 

The  connections  between  the  common  sewers  and  the  inter- 
ceptino-  sewers  were  usually  made  during  the  construction  of 
the  latter.  The  valves  of  the  inlet-pipes,  built  into  the  common 
sewers,  were  closed  and  made  tight  by  a  little  cement  around 
their  edo'es.  By  raising  these  valves  the  connection  between 
the  old  and  new  system  could  at  any  time  be  established. 


WOEKING    OF    THE    NEW    SYSTEM.  93 


CHAPTER    XI. 

WORKING    OF    THE     NEW    SYSTEM. 

January  1,  1884,  the  connections  between  the  common  and 
interceptmg  sewers  were  first  opened.  Pumping  began  at  the 
same  time,  and  tlie  sewage  was  sent  to  the  reservoir  at  Moon 
Island,  and  thence  discharged  into  the  Outer  Harbor.  Connec- 
tion with  about  one-half  of  the  common  sewers  was  made  on 
that  day,  and  most  of  the  others  were  connected  within  a  month 
thereafter ;  so  that  by  February,  1884,  nearly  all  of  the  city 
sewage  was  diverted  from  the  old  outlets.  The  upper  portion  of 
the  West  Side  intercepting  sewer,  in  Lowell  and  Causeway 
Streets,  was  built  in  1884.  The  common  sewers,  tributary  to 
it,  were  intercepted  as  construction  progressed.  A  common 
sewer  draining  a  portion  of  Dorchester,  intercepted  by  the  main 
sewer  at  East  Chester  Park  just  east  of  the  N.Y.  &  N.E. 
Eailroad,  was  not  connected  until  early  in  1885. 

Although  the  whole  intercepting  system,  therefore,  was  not 
entirely  completed  until  the  present  year,  yet  the  greater  part 
of  it  has  been  in  operation  for  fifteen  months,  — a  long  enough 
period  to  afibrd  a  fair  indication  of  its  practical  working,  and  of 
the  results  which  will  be  derived  from  it. 

As  elsewhere  stated,  the  Main  Drainage  Works  were  designed 
and  built  to  correct  two  principal  evils  inherent  in  the  old  sys- 
tem of  sewerage.     These  were  :  — 

First.  The  damming  up  of  the  common  sewers  by  the  tide, 
by  which,  for  much  of  the  time,  they  were  converted  into  stag- 
nant cesspools,  and  the  air  in  them  was  compressed,  and  to  find 
outlets  was  driven  into  house-drains  and  other  openings. 

Second.  The  discharge  of  the  sewage  on  the  shores  of  the  city 
in  the  immediate  vicinity  of  population,  thereby  causing  nui- 
sances at  many  points. 

The  first  of  these  evils  has  been  entirely  corrected  by  the  new 
system.     The  old  sewers  now  have  a  continual  flow  in  them, 


94  MAIN   DRAINAGE    WORKS. 

independent  of  the  stage  of  the  tide,  as  has  been  ascertained  by 
frequent  observations,  and  also  from  the  testimony  of  drain-lay- 
ers, who  formerly  were  only  able  to  enter  house-pipes  into  the 
the  sewers  when  the  latter  were  empty  at  low  tide,  but  now  can 
make  such  connections  at  any  time. 

The  new  system  has  also  substantially  remedied  the  second 
evil.  From  the  moment  that  any  of  the  city  sewers  was  con- 
nected with  an  intercepting  sewer,  the  sewage  which  had  before 
discharged  on  the  shore  of  the  city  was  diverted,  and  has  since 
been  conveyed  to  Moon  Island  and  emptied  into  the  Outer  Har- 
bor at  that  point. 

It  is  true  that  about  twenty-four  times  during  the  past  year, 
or  an  average  of  twice  a  month,  during  rain-storms  and  freshets, 
the  amount  of  water  flowing  in  the  sewers  has  exceeded  the 
capacity  of  the  pumps.  At  such  times  the  excess  has  been  dis- 
charged at  the  old  sewer  outlets.  But  this  occasional  and  tem- 
porary discharge  of  very  dilute  sewage  does  not  seem  to  have 
occasioned  any  nuisance.     Examinations  and  inquiries  concern- 

ino-  the  condition  of  the  shores  and  docks  at  the  sewer  outlets 

o 

have  shown  that  water,  once  continually  foul,  has  become  pure, 
bad  odors  have  ceased,  and  fish  have  returned  to  places  where 
none  had  been  seen  for  years.  The  stenches,  referred  to  by  the 
City  Board  of  Health  (p.  13),  which  formerly,  at  times,  were 
prevalent  over  the  city,  were  not  noticed  during  the  past  year. 

The  attempt  to  relieve  certain  low  districts,  subject  to  flooding 
of  cellars  during  rain-storms  at  high  tide,  b}^  discriminating  in 
favor  of  such  districts  in  respect  to  the  interception  of  storm- 
water,  has  met  with  marked  success.  No  case  of  flooding  in  such 
districts  has  been  reported  since  the  sewers  draining  them  have 
been  connected  with  the  intercepters ;  and  many  cellars,  which 
used  often  to  be  filled  several  feet  deep  with  water,  are  known 
to  have  been  perfectly  dry  during  the  past  year. 

Building  the  intercepting  sewers  has  also  dried  cellars  in  other 
parts  of  the  city  in  a  way  which  was  not  at  first  anticipated. 
When  land  on  the  shores  of  the  city  was  reclaimed  for  building 
purposes,  most  of  the  old  walls  and  wharves  were  covered  up 
by  the  new  filling.  Tide-water  followed  along  any  such  struct- 
ures through  the  ground,  and  entered  cellars  lower  than  high-tide 


WORKING    OF    THE    NEW    SYSTEM.  95 

level.  The  new  sewers  were  generally  built  along  the  present 
margins  of  the  city,  and  in  digging  deep  trenches  for  them  the 
old  structures  found  were  cut  off  and  removed.  The  backfilled 
earth  in  the  trenches  forms  an  impervious  dam  surrounding  the 
city,  beyond  which  tide-water  cannot  pass. 

The  sewers  have  been  examined  frequently  since  they  went  into 
operation.  The  average  depth  of  dry-weather  flow  in  the  inter- 
cepting sewers  is  from  ten  to  twenty  inches,  so  that  they  can  be 
entered  on  foot.  So,  also,  can  the  main  sewer  above  Tremont 
Street,  and,  sometimes,  above  Albany  Street.  Below  that  point 
the  dry-weather  flow  is  from  two  to  three  feet  deep,  necessitating 
the  use  of  a  boat. 

The  velocity  of  flow  in  the  sewers  varies  from  about  two  feet  a 
second  upwards.  An  attempt  w^as  made  to  measure  the  velocity 
at  several  ]3oints  with  a  current  meter.  While  integrating,  the 
meter  rarely  could  be  kept  under  water  longer  than  ten  seconds 
at  a  time  without  danger  of  its  being  clogged  by  paper,  hair, 
and  similar  substances.  By  the  use  of  a  stop-watch  the  instru- 
ment could  be  removed  for  cleaning  and  again  immersed  without 
interfering  with  the  experiment.  The  inclination  of  the  surface 
of  the  sewage,  though  approximately  the  same  as  that  of  the 
sewer,  was  seldom  precisely  the  same,  and  the  observations 
were  not  sufiiciently  exact,  in  any  case,  to  determine  just  what 
inclination  then  existed.  The  mean  velocity  at  the  points  of 
measurement  were,  however,  accurately  ascertained,  and  the 
results  may  be  of  sufficient  interest  to  cite. 

In  the  case  of  a  4  X  4.5  feet  sewer  (Fig.  7,  Plate  YIII.),  with 
an  inclination  of  1  in  2,000,  flowing  1.23  feet  deep,  the  mean 
velocity  was  1.9  feet  per  second.  This  sewer  had  some  graA^el 
on  its  bottom.  In  the  case  of  a  4.75  X  5.5  feet  sewer  (Fig.  8, 
Plate  VIIL),  with  an  inclination  of  1  in  2,000,  the  depth  was 
1.45  feet,  and  the  mean  velocity  was  2.45  feet  per  second.  In 
a  4.5  feet  circular  sewer,  with  an  inclination  of  1  in  700,  and 
a  depth  of  1.15  feet,  the  mean  velocity  of  flow  was  2.56  feet  per 
second.  In  the  case  of  an  8.25  feet  circular  sewer  (Fig.  14, 
Plate  VI.),  the  inclination  being  1  in  2,500  and  the  depth  1.76 
feet,  the  mean  velocity  was  2.59  feet  per  second,  sufficient  to 
keep  in  suspension  and  carry  along  all  sewage  sludge.     Most  of 


96  MAIN    DRAINAGE    WORKS. 

the  city  sewers,  when  first  intercepted,  were  found  to  contain 
deposits  of  sludge  varying  from  a  few  inches  to  several  feet  in 
depth.  All  these  deposits  were  carried  into  the  intercepting 
sewers,  and  the  sludge  reached  the  pumping-station  and  was 
pumped  up  into  the  deposit-sewers.  Gravel,  stones,  and  brick- 
bats also  were  swept  along  and  taken  out  at  the  filth-hoist. 
Fine  sand,  however,  did  not  move  so  freely,  but  settled  in 
ridges  here  and  there,  and  had  to  be  removed  by  hand. 

The  bottoms  of  the  sewers  are,  as  a  rule,  perfectly  clean.  No 
slime  accumulates  there,  or,  if  it  ever  begins  to  grow,  it  is  at 
once  scoured  off  by  the  attrition  of  moving  particles.  The  sides 
of  the  invert  below  the  surface  of  the  water  have  a  thin  coating 
of  slime,  making  them  very  slippery.  The  arch  and  the  portion 
of  the  invert  above  the  water  exposed  to  the  air  are  clean,  and 
often  quite  dry.  In  some  portions  of  the  sewers  earthy  accre- 
tions form  on  the  arch.  Where  the  sewer  is  surrounded  by 
marsh  mud  these  are  turned  black  by  sulphuretted  hydrogen, 
sometimes  they  are  colored  yellow  by  iron,  often  they  appear 
as  white  stalactites.  In  clayey  soil  the  arch  seems  to  be  about 
as  clean  as  when  laid. 

The  atmosphere  in  the  sewers  is  not  offensive,  although  a 
faint  sewage  smell  can  be  detected  on  first  entering  theru.  For 
the  first  eight  months  after  the  sewers  went  into  operation  they 
were  not  ventilated  at  the  man-holes.  This  was  because  it  was 
known  that  much  sludge  would  be  turned  into  them  from  the 
common  sewers,  and  it  was  feared  the  smell  from  it  might  be 
noticed.  Finally  the  ventilating  covers,  shown  on  Plate  VI., 
were  put  in  place.  No  smell  has  ever  been  noticed  from  them, 
and  they  considerably  improved  the  condition  of  the  atmosphere 
in  the  sewers,  which  is  now  quite  fresh  and  hardly  at  all  dis- 
agreeable ;  not  so  much  so,  for  instance,  as  is  that  in  most  railway 
carriages  after  an  hour's  use.  The  temperature  of  the  sewage 
varies  from  50°  to  65°  F.,  and  that  of  the  air  in  the  sewers  from 
40°  to  60°  F.,  depending  upon  the  outside  temperature. 

A  small  force  of  men  has  been  constantly  employed  during 
the  past  year,  in  caring  for  the  main  and  intercepting  sewers. 
This  force  has  consisted  of  a  foreman,  one  carpenter,  and  four 
laborers.     They  have  also  done  minor  items  of  work  and  repairs 


WOEKING   OF   THE   NEW   SYSTEM.  97 

which  might  properly  be  charged  to  construction.  After  every 
rain,  whenever  there  was  any  likelihood  that  water  might  have 
overflowed  at  the  old  outlets,  all  of  the  tide-gates  have  been 
visited.  As  a  rule  they  are  found  to  be  quite  tight.  Occa- 
sionally one  pair  of  a  set  (but  never  both  pairs)  are  found  to  be 
leaking  somewhat  at  high  tide.  This  is  caused  by  rags,  corks, 
pieces  of  wood,  or  other  such  matters,  catching  near  the  hinges. 
At  such  visits  the  gates  are  washed  clean,  the  hinges  greased, 
and  the  iron-work  examined  for  traces  of  incipient  rust. 

Some  of  the  tide-gates  were  made  of  white  pine  and  some  of 
spruce.  A  few  of  the  latter,  which  have  been  in  place  for  three 
years,  already  show  signs  of  deca3^  These  are  inside  gates 
situated  above  the  elevation  of  mean  tide,  so  that  they  are  com- 
paratively seldom  Avet.  To  replace  them  creosoted  lumber 
will  probably  be  used.  The  rubber  gaskets,  fastened  to  the 
gates,  are  in  perfectly  good  condition  after  about  three 
years'  use.  They  were  made  of  what  was  called  by  the  manu- 
facturer "  pure  rubber ; "  but  as  they  cost  75  cents  a  pound, 
when  crude  rubber  was  selling  at  more  than  $1.00  a  pound, 
they  probably  merely  contained  a  larger  percentage  of  that 
material  than  is  usual  in  rubber  goods.  They  were  made  with 
special  reference  to  resisting  the  effects  of  sewage  and  grease. 

The  penstocks,  flushing-gates,  and  regulators  are  also  in- 
spected periodically.  Moving  parts  are  cleaned,  slushed,  and 
moved,  so  as  to  insure  their  being  in  good  working  condition. 
The  iron,  when  carefully  painted,  does  not  appear  to  suffer 
from  rust.  About  once  in  eight  months  it  receives  a  coat  of 
asphaltum  paint.  Duplicates  ar.e  provided  of  all  pins  and  other 
small  parts,  so  that  these  can  be  taken  to  the  yard  to  be  warmed 
and  recoated.  The  chains  attached  to  the  inlet  valves,  by  which 
they  are  lifted,  are  most  subject  to  rust.  These  are  frequently 
changed  and  taken  to  the  yard,  where,  after  being  cleaned  and 
scraped,  they  are  warmed  in  a  furnace  and  coated  with  hot  pitch. 

The  catch-pails  under  the  ventilating  man-hole  covers  are 
emptied  as  occasion  demands.  In  some  localities,  and  at  some 
seasons,  pails  will  be  filled  in  less  than  a  month.  Others  will 
not  require  attention  for  three  months.  Men  drive  along  the 
sewer  line  with  a  cart,  remove  a  man-hole  cover,  lift  out  the 


98  MAIN   DRAINAGE    WORKS. 

pail,  empty  its  contents  into  the  cart,  and  again  replace  the  pail 
and  cover.  A  few  extra  pails  are  carried  in  the  cart,  so  that 
if  any  of  those  in  use  shows  signs  of  rust  it  can  be  replaced  by 
another,  and  be  taken  to  the  yard  for  cleaning  and  recoating. 

The  filth-hoist  at  the  pumping-station  seems  satisfactorily  to 
answer  the  purpose  for  which  it  was  designed.  In  dry  weather 
the  cages  are  raised  three  times  a  day,  and  the  average  daily 
yield  from  them  is  about  16  cubic  feet.  The  matters  inter- 
cepted are,  rags,  paper,  corks,  half  lemons,  lumps  of  fat,  dead 
animals,  pieces  of  wood,  bottles,  children's  toys,  pocket-books, 
and  such-like  miscellaneous  articles,  which  by  accident  or  design 
are  thrown  into  house-pipes .  Comparatively  little  solid  fecal  mat- 
ter is  caught,  as  most  of  it  dissolves  before  reaching  this  point. 

When  it  rains,  and  deposits  are  scoured  out  of  the  old  sewers, 
very  much  more  filth  is  caught  in  the  cages.  The  amount  some- 
times equals  three  or  four  cubic  yards  in  24  hours.  At  such 
times  it  is  necessary  to  raise  and  clean  the  cages  every  half-hour, 
during  the  night  as  well  as  in  the  day,  in  order  to  prevent  their 
becoming  clogged  and  backing  up  the  sewage  in  front  of  them. 

At  first  what  was  removed  from  the  cages  was  buried  in  pits 
near  the  pumping-station.  This  not  being  considered  a  satis- 
factory method  of  disposal  an  attempt  was  made  to  burn  the 
filth  in  the  furnaces  under  the  boilers.  It  was  found  that  the 
filth,  as  taken  from  the  cages,  contained  so  much  water  that  the 
fires  were  injured.  Accordingly  a  simple  press,  like  a  cider 
press,  was  procured,  by  which  most  of  the  water  was  pressed 
out.  The  comparatively  dry  cakes  remaining  after  pressing 
are  now  burned  without  injuriously  affecting  the  furnace  fires. 

The  two  high-duty  "  Leavitt "  pumping-engines  and  the  two 
storm-duty  "  Worthington  "  pumping-engines  have  all  been  run 
more  or  less  during  the  past  j^ear.  Any  one  of  them  is  able  to 
pump  the  ordinary  dry-weather  flow  of  sewage.  As  a  rule  one 
of  the  Leavitt  engines  is  kept  running  ;  should  it  rain,  and  addi- 
tional pumping  capacity  be  needed,  the  second  Leavitt  engine 
is,  by  preference,  started  ;  if  still  more  capacity  is  needed,  the 
Worthino-ton  engines  are  started.  When  the  amount  of  water 
arriving  by  the  sewer  decreases,  the  Worthington  engines  are 
first  stopped. 


WORKING    OF    THE    NEW    SYSTEM. 


99 


The  average  daily  quantity  of  sewage  pumped  in  dry  weather 
is  about  24,000,000  gallons,  and  the  average  number  of  tons  of 
coal  consumed  in  doing  the  work  is  about  3^.  This,  with 
some  steam  used  for  other  purposes,  gives  a  working  duty  in 
the  case  of  the  Leavitt  engine,  of  about  95,000,000  pounds" 
raised  1  foot  high  by  the  consumption  of  100  pounds  of  coal. 
The  Worthington  engines,  under  similar  conditions,  show  a 
working  duty  of  somewhat  more  than  50,000,000  foot-pounds. 

The  following  table  gives  the  results  of  the  first  year's  pump- 
ing, beginning  with  February,  1884,  when  the  works  had  got 
fairly  into  operation  :  — 


Daily 
Average 
Gallons 
Pumped. 

Daily 
Average 

Pounds 
op  Coal. 

Per 
Cent. 

op 
Ashes. 

Gallons 

Pumped 

PER  Pound 

op  Coal. 

Rainfall. 

Month. 
1884. 

Inches. 

Number 
of  Days 
it  Rained. 

February   .     . 

25,777,360 

14,028 

15.8 

1,836 

5.74 

20 

March  .     .     . 

32,437,379 

18,880 

14.8 

1,709 

4.86 

19 

April     .     .     . 

29,949,356 

15,671 

16.2 

1,913 

4.76 

17 

May.     .     .     . 

25,121,056 

13,127 

15.6 

1,915 

3.31 

11 

June      .     .     . 

26,712,298 

13,265 

16.5 

2,015 

4.01 

7 

July.     .     .     . 

25,900,400 

13,529 

19.2 

1.912 

4.25 

17 

August .     .     . 

31,674,621 

14,704 

16.0 

2,174 

5.01 

14 

September 

28,412,431 

11,099 

12.1 

2,568 

.31 

8 

October      .     . 

27,601,557 

10,206 

13.3 

2,698 

3.17 

13 

November .     . 

27,501,283 

8,985 

8.0 

3,073 

3.03 

9 

December  .     . 

30,883,501 

10,181 

7.2 

2,885 

4.46 

15 

1885. 

January      .     . 

38,498,668 

11,448 

7.2 

3,265 

5.33 

9 

It  will  be  seen  that  the  daily  average,  as  given,  is  larger  than 
the  dry-weather  flow,  because  it  includes  the  extra  quantities 
pumped  during  rains.  The  largest  day's  work  thus  far  has 
been  81,280,883  gallons,  but  for  a  few  hours  this  rate  has 
been  much  exceeded.  Until  August,  1884,  the  pumping  was 
not  done  economically.     At  that  time  a  change  was  made  in 


100  MAIN   DEAINAGE   WORKS. 

the  nianaofement  of  the  station,  with  a  considerable  increase  in 
economy.  A  further  gain  was  made  in  November,  1884,  by 
substituting  bituminous  coal  for  anthracite,  which  had  pre- 
viously been  used.  The  former  coal  makes  more  steam,  and 
costs  about  $1  less  a  ton.  The  comparatively  lovv  duty  shown 
by  the  table  for  December  was  due  to  the  fact  that  the  Worth- 
ington  engines  were  largely  used  during  that  month,  while  a 
temporary  building  over  the  Leavitt  engines  was  being  taken 
down. 

There  are  no  means  for  determining  accurately  the  actual 
amount  of  the  city  water  supply  in  the  district  whose  sewers 
are  tributary  to  the  Main  Drainage  System.  But  it  is  evident 
that  even  in  dry  weather  the  amount  of  sewage  reaching  the 
pumpin£::-station  by  the  main  sewer  is  greater  than  the  water- 
supply  of  the  districts  drained  by  it.  The  excess  is  not  con- 
stant ;  sometimes  it  is  estimated  to  be  10  per  cent,  of  the 
whole,  and  at  other  times  it  is  probably  25  per  cent.,  or 
even  more.  This  excess  comes  from  several  sources.  Many 
dwellings  and  factories  in  sewered  districts  have  private  water 
supplies.  Breweries,  and  other  similar  large  establishments,  con- 
tribute largely  in  this  way.  A  single  sugar  refinery  was  found 
to  pump  and  use,  daily,  about  1,000,000  gallons  of  salt  water, 
all  of  which  properly  might  have  gone  back  into  the  harbor, 
but  was,  instead,  turned  into  the  sewers.  In  the  spring,  when 
the  ground  is  full  of  water,  much  of  it  leaks  into  the  common 
sewers,  and  is  by  them  carried  to  the  intercepters.  Sea-water 
also,  at  high  tide,  finds  its  way  along  some  of  the  old  box-sew- 
ers, and  leaks  into  them  back  of  the  tide-gates.  It  will  prob- 
ably prove  to  be  true  economy  to  rebuild  many  of  the  old 
sewers,  in  whole  or  in  part. 

The  permanent  working  force  employed  at  the  pumping- 
station  at  present  is  as  follows  :  — 

1  Chief  Engineer, 

3  Assistant  Engineers, 

9  Oilers, 

3  Firemen, 

3  Coal-passers, 

1  Clerk. 


WORKING    OF    THE    NEW    SYSTEM.  101 

The  men  employed  in  the  filth-hoist,  included  in  the  above, 
rank  as  oilers.  The  administration  at  this  point  is,  of  course, 
not  as  economical  as  it  would  be  if  there  were  a  uniform, 
constant  amount  of  work  to  be  done. 

The  deposit-sewers  have  perfectly  answered  their  purposes 
in  arresting  all  heavy  matters  contained  in  the  sewage.  The 
cross-sectional  area  of  these  sewers  is  so  large,  and  the  result- 
ing velocity  of  flow  is  so  sluggish,  even  when  four  pumps  are  run- 
ning, that  all  suspended  matters  subside  before  reaching  the 
tunnel.  Sand  and  gravel  are  deposited  at  once,  as  soon  as  they 
enter  the  sewers  ;  lighter  substances  are  carried  a  little  farther ; 
but  only  floating  matters  or  those  having  about  the  same  spe- 
cific gravity  as  water,  remain  in  suspension  long  enough  to  reach 
the  further  end  of  the  sewers. 

As  elsewhere  stated,  the  sludge,  contained  by  the  common 
sewers  at  the  time  connection  was  made  between  them  and 
the  intercepting  sewer,  passed  to  the  pumping-station  and  was 
pumped  -into  the  deposit- sewers.  The  amount  of  this  was 
12,000  cubic  yards,  or  more.  The  best  way  of  removino-  it  was 
long  considered,  and  it  was  only  in  the  autumn  of  1884  that 
the  appliances  described  in  Chapter  VIII.  were  adopted  and 
constructed.  When  the  six-inch  pipe  connecting  one  deposit- 
sewer  with  the  sludge-tank  was  first  opened,  the  deposits  near 
where  the  pipe  entered  the  sewer  were  drawn  into  the  tank, 
which  in  the  space  of  two  days  was  filled  with  about  100  yards 
of  sludge. 

The  floating  scrapers  (Plate  XIX.)  were  not  completed  un- 
til the  winter.  They  work  very  well,  with  a  combined  scrap- 
ing and  flushing  action,  and  by  their  use  the  sand  and  gravel 
deposits  can  be  moved  from  one  end  of  the  sewer  to  the  other. 
The  sludge-tank  was  filled  a  second  time,  principally  w^ith  clear 
sand,  when  operations  were  stopped  by  the  harbor's  freezing  * 
over.  The  bay  remained  closed  by  ice  until  early  in  March, 
when  the  removal  of  the  deposits  was  again  resumed.  It  seems 
probable  that  this  method  of  removal  will  prove  as  satisfactory 
as  any  which  could  be  adopted. 

As  the  tunnel  is  142  feet  below  the  harbor,  and  has  been  con- 
stantly full  of  sewage  since  pumping  began,  there  has  been  no 


102  MAIN    DRAINAGE    WORKS. 

opportunity  for  inspecting  it.  For  the  first  few  months  of  1884, 
before  all  of  the  city  sewers  had  been  intercepted,  a  compara- 
tively small  amount  of  sewage  was  pumped,  especially  at  night. 
At  such  times  the  velocity  of  flow  through  the  tunnel  was  very 
slight,  often  less  than  one-half  of  a  foot  a  second.  Occasionally 
pumping  would  be  stopped  for  a  few  hours  at  night,  to  allow 
the  sewage  to  accumulate.  At  present  the  ordinary  flow  in  the 
tunnel  is  seldom  faster  than  1  foot  a  second.  As  J;he  sewage  takes 
from  two  to  four  hours  to  pass  through  the  tunnel,  at  these  slow 
velocities,  it  was  to  be  expected  that  deposits  would  occur  there. 

To  ascertain  the  extent  of  such  deposits,  and  whether  they 
were  likely  to  become  permanent,  some  experiments  were  made. 
These  were  based  upon  the  following  laws  : 

That  the  flow  through  the  tunnel  is  produced  by  the  differ- 
ence in  elevation  of  the  water  at  its  two  ends ; 

That  the  amount  of  this  difierence  is  a  measure  of  the  fric- 
tional  resistance  which  the  tunnel  opposes  to  the  flow  of  the 
sewage ; 

That,  in  proportion  as  the  water-way  of  the  tunnel  is  ob- 
structed by  deposits,  the  resistance,  and  therefore  the  difference 
in  elevation  of  the  water  at  its  two  ends,  will  be  greater  than 
they  would  be  if  the  tunnel  was  clean. 

The  method  of  making  the  experiments   was  as  follows  :  — 

The  quantity  of  water  passing  through  the  tunnel  was  ascer- 
tained by  pump  measurement,  with  allowance  for  slip.  The 
diflference  in  elevation  at  the  two  ends  of  the  tunnel  was  deter- 
mined by  means  of  sliding  gauges,  with  knife  edges  where  they 
came  in  contact  with  the  surface  of  the  water. 

The  coeflicient  was  then  calculated  for  the  formula 

V  :=:  C  l/El  or  C  =  r^ 

in  which 

Y  —  Velocity  in  feet  per  second 

area 


R  =r  Hvdraulic  mean  radius 


wet  perimeter 

I  =  Sine  of  inclination  =  -j — '^--r- 

length 

C  =3  A  coe6&cient  ascertained  by  experiment. 


WORKING    OF    THE    NEW    SYSTEM.  103 

As  the  tunnel  is  circular,  7.5  feet  in  internal  diameter,  the 
value  of  R,  corresponding  to  the  full  cross-sectional  area,  is  1.875 
feet.  Experiments  on  the  flow  of  water  in  the  Sudbury-River 
Conduit,'  which  was  a  brick  structure  like  the  tunnel,  gave  a 
coefficient  corresponding  to  R  =  1.875,  of  about  137.  It  was 
not  anticipated  that  the  coefficient  found  for  the  tunnel,  even 
when  it  was  clean,  would  be  quite  so  large  as  that  of  the  con- 
duit ;  since  the  surface  of  the  former  is  somewhat  rougher,  and 
some  loss  of  head  would  be  occasioned  by  changes  in  direction 
at  bends  and  by  obstructions  at  the  east  shaft. 

It  was  also  expected  that  the  coefficient  would  vary  somewhat 
with  the  velocity  and  with  the  dilution  of  the  sewage.  Under 
the  most  favorable  circumstances,  with  the  tunnel  free  from 
depo.sits,  the  coefficient  would  approximate  137,  being  that 
found  by  the  experiments  above  mentioned. 

The  full  area  of  the  tunnel  was  used  in  determining  the  values 
ofVandR.  This  assumed  that  the  tunnel  was  clean.  Should 
the  coefficient  be  found  to  be  nmch  lower  than  that  anticipated, 
it  would  show  that  the  foregoing  assumption  was  incorrect,  and 
that  the  area  of  the  tunnel  was  partly  obstructed. 

Whatever  was  the  true  value  of  the  coefficient,  its  increase  or 
decrease,  as  determined  by  successive  experiments  under  the 
same  conditions,  would  show  whether  the  amount  of  deposit  in 
the  tunnel  was  becoming  less  or  greater. 

Arrangements  are  provided  for  flushing  the  tunnel  by  running 
four  pumps  simultaneously,  salt  water  being  admitted  to  the 
pump-wells  to  supply  any  deficiency  of  sewage.  The  volume 
pumped  is  generally  at  the  rate  of  about  114,000,000  gallons  per 
day,  which  gives  a  velocity  of  about  four  feet  per  second  through 
the  tunnel. 

The  first  flushing  with  four  pumps  was  done  June  12,  1884. 
Just  previous  to  this  time,  by  two  measurements  on  different 
days,  the  loss  of  head  through  the  tunnel  was  ascertained  to  be 
about  .54  of  a  foot,  and  the  values  of  C  were  found  to  be  CO  and 
82.     On  June  13,  the  day  after  flushing,  an  experiment,   with 

1  Traasactions  of  the  American  Society  of  Civil  Engineers,  Vol.  XII.,  No,  CCLIII. 


104  MAIN    DRAINAGE    WORKS. 

the  same  conditions  as  those  previously  made,  gave  a  loss  of 
head  of  .30  of  a  foot,  and  a  value  of  C  =  110. 

This  value  was  still  too  low  to  indicate  an  entirely  clean  tun- 
nel, but  showed  that  the  water-way  had  been  increased  by  a 
removal  of  a  portion  of  the  deposit  by  the  flushing.  This  was 
known  to  be  a  fact,  since  the  sludge  scoured  out  by  the  flushing 
had  been  observed  in  the  reservoir.  Inspection  showed  that 
the  deposit  carried  into  the  reservoir  was  of  a  very  light  nature, 
containing  soft  mud,  horse-manure,  water-logged  match  ends, 
bits  of  lemon-peel,  paper,  and  similar  substances. 

Beginning  in  June,  1884,  flushing  with  four  pumps  has  been 
done  regularly  about  once  a  fortnight.  At  four  different  times 
measurements  to  determine  the  value  of  G  have  been  made 
during  the  flushing.  At  such  times  the  velocity  of  flow  is  high, 
and  from  75  to  80  per  cent,  of  the  volume  pumped  is  clean  salt 
water,  aflbrdins^  conditions  favorable  for  obtaininsf  a  hio;h  co- 
efficient.  The  values  of  C,  derived  from  these  several  experi- 
ments, were  as  follows  :  — 

June  12,  1884.  C  =  129. 

Oct.  20,  1884.  C  =  120.7. 

Jan.   15,  1885.  C  =  146.3. 

Feb.  16,  1885.  C  =  146.6. 

The  last  two  experiments  were  made  on  days  following  periods 
when  the  quantity  of  sewage  pumped  had  been  unusually  large, 
on  account  of  rain  and  melting  snow,  which  may  account  for  the 
laro^eness  of  the  coefficients.  There  mav,  also,  have  been  some 
unusual  slip  in  the  valves.  There  can  be  little  doubt,  however, 
that  at  this  time  the  water-way  of  the  tunnel  was  not  appreci- 
ably obstructed. 

Since  these  were  experiments  on  the  flow  through  a  large  pipe 
they  may  have  some  general  interest  for  engineers,  and  their 
details  are  given  in  the  following  table  :  — 


WORKING    OF    THE    NEW    SYSTEM. 


105 


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106  MAIN   DRAINAGE   WORKS. 

The  wooden  flume  between  Squantum  and  Moon  Island  has 
been  watched  carefully  durmg  the  past  year.  It  was  at  first 
tight,  but  the  efiect  of  the  summer's  sun  lying  on  one  side  of  it 
tended  to  make  the  planks  shrink  and  warp  somewhat,  so  that 
leakage  occurred  in  some  places.  These  were  stopped  by 
tightening  the  bolts  and  wedges,  and  by  fastening  the  corner 
bottom  planks  to  the  sides  with  lag  screws.  To  guard  against 
the  sun  the  flume  was  given  a  second  coat  of  paint.  Putting  a 
cheap  roof  over  it  would,  doubtless,  prolong  the  duration  of  its 
efiective  service. 

When  the  sewage  in  the  reservoir  is  low,  the  flume  runs 
about  half-full.  As  the  basins  fill,  the  depth  of  flow  increases 
until  finally  it  runs  entirely  full,  acting  as  a  pipe.  The  ordi- 
nary velocity  of  flow  is  about  three  feet  a  second,  or  less  as  the 
depth  increases.  Twice  a  day,  when  the  reservoir  is  flushed,  as 
described  later  on,  the  current  through  the  lower  end  of  the 
flume  attains  the  remarkable  velocity  of  about  seven  feet  a  second. 
This  velocity  is  sufiicient  to  move  stones  and  brickbats. 

Nevertheless  the  flume  is  not  clean.  From  its  bottom  up  to 
the  ordinary  flow  line  the  sides  are  covered  with  a  slimy  deposit 
from  one-eighth  to  one-quarter  of  an  inch  in  thickness.  Above 
the  middle  and  on  the  top  there  is  also  some  slime,  but  not  so 
much  as  below.  The  condition  of  this  sewer  is  commended  to 
the  attention  of  those  sanitarians  who  are  accustomed  to  repre- 
sent flushing  as  a  certain  remedy  for  the  accumulation  of  slime 
in  pipes. 

Some  experiments  were  made  to  determine  the  value  of  C  in 
the  formula  V  =;  C  a/RI  as  applied  to  the  flume.  In  one  trial? 
the  flume  flowing  about  half-full  with  sewage,  the  value  of  E, 
was  1.45  feet,  the  velocity  was  2.94  feet  a  second,  and  the  value 
of  C  was  found  to  be  116.9.  In  a  second  trial,  under  similar 
conditions,  the  following  values  were  obtained  :  E,  =  1.41  ;  V  = 
2.87;  C=116.6.  In  a  third  trial,  when  four  pumps  were  running 
and  the  flume  was  flowing  full,  75  to  80  per  cent,  of  the  water 
pumped  being  clean  salt  water,  the  values  of  R,  V,  and  C  respect- 
ively, were  1.5,  4.80,  and  134.8.  It  will  be  noticed  that  the 
value  of  R  was  about  the  same  in  the  last  trial  as  in  the  first  two, 
but  that  the  value  of  C  was  very  much  greater.    It  is  thought  that 


WORKING    OF    THE    NEW    SYSTEM.  107 

this  may  be  due  to  the  fact  that  the  first  trials  were  made  with 
clear  sewage,  whereas,  in  the  case  of  the  last  trial,  the  water  was 
comparatively  clean.  It  seems  reasonable  to  suppose  that  some 
head  would  be  expended  in  maintaining  in  suspension  the  solid 
particles  contained  by  the  sewage.  The  subject  is  worthy  of  fur- 
ther investigation,  because  it  concerns  the  applicability  to  the 
flow  of  sewage  of  hydraulic  formulae  derived  from  experiments 
on  the  flow  of  clean  water. 

The  reservoir  has  a  capacity  of  25,000,000  gallons.  As  sew- 
age is  stored  in  it  for  about  ten  hours  at  a  time,  between  the 
end  of  one  period  of  discharge  and  the  beginning  of  another,  the 
basins,  as  a  rule,  have  been  filled  only  about  half-full  during 
the  past  year.  The  process  of  discharging  is  begun  about  one 
hour  after  the  begimiing  of  ebb  tide.  By  this  time  the  surface 
of  the  sea  is  as  low  as  the  bottom  of  the  reservoir,  and  a  good 
harbor  current  is  setting  outwards  past  the  outlet.  Water  is 
admitted  to  the  turbine,  and  by  the  power  transmitted  from  it 
the  upper  gates  in  the  outfall  sewer  are  first  closed.  The  sew- 
age then  arriving  is  thus  stored  in  the  sewer,  and  its  surface 
rises  several  feet.  Meantime  the  lower  gates  in  the  discharge 
sewer  are  opened,  and  the  sewage  in  the  reservoir  flows  through 
them  to  the  outlet.  Under  ordinary  circumstances  the  basins 
are  emptied  in  about  30  minutes. 

There  is  left  in  the  basins  a  thin  deposit  of  semi-fluid  mud, 
generally  about  one-quarter  of  an  inch  thick,  but  in  greater  quan- 
tity after  storms.  To  remove  this,  flushing  is  first  resorted  to. 
During  the  past  year  four  brick  pai'tition-walls  were  built  across 
the  gallery  between  the  sewers  and  the  reservoir.  One  of  these 
was  built  opposite  the  middle  of  each  basin.  As  soon  as  a  basin 
is  empty  an  upper  gate  is  opened  on  one  side  of  the  divid- 
ing wall  just  mentioned,  and  the  lower  gates  on  the  other  side 
of  it.  The  sewage,  which  has  by  this  time  accumulated  to 
a  considerable  depth  in  the  outfall  sewer,  passes  through  the 
openings  into  one  side  of  the  basin,  and  flows  with  moderate 
force  up  the  gutters  to  the  back  retaining-wall .  As  the  gutters 
fill  the  sewage  overflows  across  the  ridges  and  down  the  gutters 
on  the  other  side  of  the  basin.  Much  of  the  sludge  is  in  this 
wav  washed  ofi"  into  the  o-utters  and  carried  into  the  discharge 


108  MAIN    DRAINAGE    WORKS. 

sewers.  The  flushing  is  done  alternately  from  one  and  the 
other  side  of  the  basin. 

If  a  basin  cannot  thus  be  entirely  cleaned,  men  descend  into 
it  with  broad  wooden  scrapers,  convex  on  one  side,  to  fit  the 
gutters,  and  flat  on  the  other.  With  these  the  mud  is  scraped 
into  the  gutters  and  pushed  down  into  the  gallery,  whence  it 
is  washed  out  into  the  sea  at  the  next  time  of  discharge.  Such 
cleansing  operations  occupy  about  one-half  hour  for  each  basin, 
and  are  not  especially  disagreeable  for  the  men.^ 

When  the  sides  of  a  basin  need  cleaning  the  pump  in  the 
engine-house  is  started,  and  one  or  more  lines  of  hose  are 
coupled  to  the  hydrants  on  the  4-inch  pipe  fastened  to  the  floor 
in  the  middle  of  each  basin.  The  pump  will  give  two  strong 
fire  streams  with  sufficient  force  to  wash  ofi"  any  crust  which  has 
hardened  on  the  walls.  The  streams  can  also  be  used  in  con- 
nection with  scraping  and  washing  the  floors  of  the  basins. 

The  first  sewao;e  which  discharo;es  at  the  outlet  contains  a 
considerable  amount  of  sludge  which  has  settled  in  the 
gallery  and  discharge  sewers,  and  gives  to  the  effluent  a  dark, 
muddy  appearance.  After  a  few  minutes  the  color  is  somewhat 
lost,  and  the  effluent  looks  like  moderately  dirty  water. 

Its  efiect  in  discolorino^  the  salt  water,  and  its  course  as  it 
joins  the  current  out  of  the  harbor,  can  be  plainly  noticed. 
Being  fresh  water  it  rises  to  the  surface,  and  when  a  half-mile 
from  the  outlet  seems  to  lie  on  top  of  the  salt  water  in  a 
stratum  but  a  few  inches  thick.  The  greasy  nature  of  the  sew- 
age tends  to  quiet  the  ripples  commonly  seen  on  the  surface  of 
the  harbor,  so  that  the  area  affected  by  the  discharge  is  plainly 
determined.  From  experiments  with  floats  it  is  known  that 
the  sewage  travels  nearly  five  miles,  following  the  Western  Way 
and  Black-Rock  Channel  out  to  the  vicinity  of  the  Brewster 
Islands.  By  the  time  it  has  travelled  a  mile  from  the  outlet 
most  of  the  color  is  lost,  and  by  the  time  it  has  gone  two  miles 
(before  passing  Rainsford  Island)  not  the  slightest  trace  of  it 
can  be  distino-uished. 

^  Since  this  was  written  slight  changes  have  been  made  in  the  method  of  flushing  the 
floors  and  gutters,  which  render  the  operation  so  efiective  that  it  is  no  longer  necessaiy 
to  send  men  into  the  basins  to  clean  them. 


WORKING    OF    THE    NEW    SYSTEM.  109 

When  the  works  went  into  operation,  and  for  the  first  nine 
months  thereafter,  there  were  no  gates  near  thfe  outlet  at  the 
end  of  the  discharge  sewers.  As  a  consequence  the  last  por- 
tion of  sewage  from  the  reservoir,  filling  the  discharge  sewers, 
flowed  out  into  the  harbor  slowly  as  the  tide  fell.  This  was 
the  dirtiest  part  of  the  sewage,  because  it  contained  scourings 
from  the  basins.  By  referring  to  the  plan  (Plate  Y.)  it  will  be 
seen  that  a  cove  was  formed  between  the  island  and  the  pier 
containing  the  discharge  sewers.  In  this  cove  a  foot  or  more 
of  sludge  accumulated.  A  thin  layer  of  sludge  also  formed  on 
the  beach  between  the  outlet  and  the  extreme  point  of  the 
island.  This  last-named  deposit  was  only  found  between  the 
levels  of  mid-tide  and  low  water. 

In  winter  no  smell  comes  from  these  deposits,  and  in  sum- 
mer none  is  noticed  except  during  low  tide.  On  three  occa- 
sions last  summer,  when  the  wind  was  from  the  east,  the 
smell  was  so  strong  as  to  be  noticed  at  Squantum,  a  mile 
away. 

In  hopes  of  preventing,  or  at  least  lessening,  the  formation 
of  such  deposits,  a  set  of  gates  have  been  placed  in  the  cham- 
ber at  the  outlet.  By  these  the  sewage  filling  the  discharge 
sewers  is  held  back  until  the  beo-innino;  of  the  succeedino-  dis- 
charge,  when  it  is  forced  out  into  a  good  current.  These  gates 
have  not  been  in  place  long  enough  to  show  how  much  they 
will  accomplish  ;  but,  should  objectionable  deposits  still  continue 
to  form  on  the  island,  it  is  thought  that  an  efifectual  remedy 
can  be  provided.  This  will  consist  in  building  a  solid  bulk- 
head wall  near  the  line  of  low  water,  from  the  outlet  to  the  ex- 
treme easterly  point  of  the  island.  Such  a  structure  could  be 
built  for  $30,000. 

No  trace  of  the  sludge  has  been  found  on  the  shores  in  any 
other  part  of  the  harbor.  Very  little  smell  emanates  from  the 
reservoir  in  cool  weather ;  not  enough  to  be  perceptible  at  a 
contractor's  boarding-house,  about  200  feet  distant.  In  sum- 
mer the  smell  is  more  noticeable  ;  but  not  nearly  so  much  so  as 
is  that  arising  from  the  deposits  of  sludge  on  the  beach . 

As  a  whole,  the  Main  Drainage  System  works  well,  and  no 
radical  defect  has  been  detected  in  any  portion  of  it.     It  is  not 


110  MAIN   DRAINAGE   WORKS. 

claimed  that,  by  itself,  it  furnishes  a  perfect  system  of  sewer- 
age for  the  city.  Many  defective  house-drains  and  common 
sewers  still  exist,  and  must  in  time  be  replaced ;  but  the  new 
system  provides  an  outlet  for  the  rest,  without  which  other  re- 
forms would  be  comparatively  useless. 

By  building  the  Main  Drainage  Works,  Boston  has  taken 
the  first,  most  essential  step  in  the  direction  of  efficient  sewer- 
age. 


APPENDIX. 


APPENDIX  A. 


RECORD    OF    TESTS    OF   CEMENT    MADE     FOR    BOSTON 
MAIN  DRAINAGE   WORKS. 

1878-1884.1 

The  Main  Drainage  Works  chiefly  consist  of  brick,  stone,  and  con- 
crete masonry.  About  180,000  barrels  of  cement  were  required  to 
build  this  masonry ;  and  to  insure  its  stability  and  durability  it  was 
necessary  that  the  cement  should  be  of  good  quality.  From  the  start, 
therefore,  means  for  determining  the  qualities  of  all  cements  used  or 
offered  for  use  were  provided.  A  room  was  set  apart  for  these  oper- 
ations and  an  inspector  appointed  to  conduct  them. 

The  tests  were  devised,  principally,  in  order  to  determine  three 
points,  namely :  — 

1.  The  relative  strength  and  value  of  any  cement  as  compared 
with  the  average  strength  and  value  of  the  best  quality  of  similar 
kinds  of  cements. 

2.  The  absolute  and  comparative  strength  and  value  of  mortars  of 
different  kinds  made  from  the  same  cement. 

3.  The  effect  produced  upon  the  strength  of  any  cement  mortar  by 
different  conditions  and  methods  of  treatment. 

This  knowledge  was  chiefly  sought  by  observations  of  the  tensile 
strength  of  the  cements  and  mortars  tested.  Reasons  for  adopting 
the  tensile  test  were,  that  it  required  comparatively  light  strains  to 
produce  rupture  ;  that,  as  it  was  universally  used,  it  afforded  results 
which  could  be  compared  with  those  of  other  observers  ;  and,  finally, 
because  the  tensile  stress  is  precisely  that  by  which  the  mortar  of 
masonry,  in  most  cases  of  failure,  actually  is  broken. 

All  the  particles  of  any  cement  are  of  appreciable  size,  and  its 
strength  as  a  mortar  depends  on  the  extent  to  which  the  particles  ad- 
here, at  their  points  of  contact,  to  each  other  or  to  some  inert  substance. 
This  adherence  may  be  overcome  and  the  mortar  broken,  either  by 
pulling  the  particles  apart  by  tension,  or  by  pushing  them  past  each 

'  A  paper  presented  to  the  American  Society  of  Civil  Engineers, 


114  MAIN    DRAINAGE    WORKS. 

other  by  compression.  The  effect  upon  the  adhering  quality  of  the 
particles  is  not  very  different  in  the  two  operations  ;  but  in  the  latter 
the  friction  of  the  particles  against  each  other  must  also  be  overcome, 
which  requires  the  application  of  very  much  more  force.  Transverse 
tests  are  only  tensile  tests  differently  applied,  and  shearing  produces 
a  stress  intermediate  to  tension  and  compression.  When  masonry  is 
strained,  one  part  of  it  is  in  tension,  another  in  compression,  and,  as 
mortar  yields  more  readily  to  tensile  stress,  failure  generally  occurs 
by  rupture  of  the  joints  in  tension. 

Briquettes  for  testing,  with  a  breaking  section  of  one  square  inch, 
were  first  used  ;  but  it  was  thought  that  these,  from  their  small  size, 
were  liable  to  be  strained  and  injured  by  handling  in  taking  them 
from  the  moulds  and  transferring  them  to  the  water.  A  larger  pat- 
tern, with  a  breaking  section  one  and  one-half  inches  square,  or  two 
and  one-quarter  square  inches,  was  finally  adopted.  Comparative 
tests  with  briquettes  of  one  inch  and  two  and  one-quarter  inches  sec- 
tion respectively  indicated  that  there  was  little,  if  any,  difference  in 
their  strength  per  square  inch. 

The  shape  of  the  briquette  adopted  is  shown  by  Fig.  2,  Plate  XXVIII. 
Fig.  1  of  the  same  plate  shows  the  brass  moulds  in  which  the  mortar 
was  packed  to  form  the  briquettes.  These  moulds  proved  very  sat- 
isfactory. They  were  strong,  and  easily  clamped  and  opened.  The 
clamp  consisted  of  a  piece  of  brass  wire  riveted  loose  in  the  project- 
ing lug  of  one  branch  of  the  mould,  and  binding  by  friction  when 
turned  against  the  wedge-shaped  lug  on  the  other  branch.  If  a  fast- 
ening worked  loose  a  single  tap  of  the  hammer  would  tighten  it.  All 
breaking  loads  were  reduced  to  pounds  per  square  inch  of  breaking 
section  by  multiplying  by  four  and  dividing  by  nine. 

Before  testing  a  cement  its  color  was  first  observed.  The  absolute 
color  of  a  natural  cement  indicates  little,  since  it  varies  so  much  in 
this  particular.  But,  for  any  given  kind,  variations  in  shade  may  indi- 
cate differences  in  the  character  of  the  rock  or  in  the  degree  of  burn- 
ing. With  Rosendale  cements  a  light  color  generally  indicated  an 
inferior  or  underburned  rock.  An  undue  proportion  of  underburned 
material  was  indicated  in  the  case  of  Portland  cement  by  a  yellowish 
shade,  and  a  marked  difference  between  the  color  of  the  hard-burned, 
unground  particles  retained  by  a  fine  sieve  and  the  finer  cement  which 
passed  through  the  sieve. 

The  weight  per  cubic  foot  was  also  sometimes  ascertained.  As  this 
would  vary  with  the  density  of  packing,  a  standard  for  comparison 
was  adopted,  which  was  the  density  with  which  the  cement  would 
pack  itself  by  an  average  free  fall  of  three  feet.     The  apparatus  used 


Plate   XXVIII. 


B  Ff  A    S  S  MOULD 

F/o.  /. 


BH/QUETTE. 


PAT  OF  CEMENT 
TES  TED  FOR  CHECK  CRA  CKS. 


TUBE  AND  BOX 
FOBWEtGH/NG  CEMENT. 


Fig.  a. 


Fig.  4. 


PAN  FOR  KEEPING  BR/QUETTES. 


Fig.  3. 


Fig.  7. 


UGHT  &  HE  A  VY  WIRES. 
Fig.  5. 


Fig.  e. 


SCOOP 


m  iif Mlin'iiiaiaiiiBll^fcp    FiG.  8. 


FOP  TAKING  SAMPLES  FROM  BARRELS. 


BARREL  OF  CEMENT 
60PER  CENT  FINE 


Fig.  9. 


40 PER  CENT 


eOPEP  CENT 


BARREL  OF  CEMENT 
SUPER  CENT  FINE 

sandM^^^^^  ioper  cent 


90PER  CENT 


APPENDIX    A.  115 

is  shown  by  Fig.  3,  Plate  XXVIII.  Tlie  cement  was  placed  in  a 
coarse  sieve  on  the  top  of  a  galvanized  iron  tube,  and,  the  sieve  being 
shaken,  the  cement  sifted  through  the  tube  into  the  box  below.  This 
box  held  exactly  one-tenth  of  a  cubic  foot  when  struck  level  with  its 
top. 

The  weights  per  cubic  foot  as  determined  by  this  method  varied 
considerably  with  different  kinds  and  brands  of  cement,  and  some- 
what with  different  samples  of  the  same  brand.  The  averages  were 
as  follows  :  — 

Table  No.  1. 

Rosendale i9     to  56  pounds. 

Lime  of  Tell 50 

Roman 54 

A  fine-ground  French  Portland 60 

English  and  German  Portlands 77.5  to  87 

An  American  Portland 95 

The  following  table  shows  the  effect  of  fine  grinding  upon  the 
weight  of  cement.  It  gives  the  weight  per  cubic  foot  of  the  same 
German  Portland  cement,  containing  different  percentages  of  coarse 
particles,  as  determined  by  sifting  through  the  No.  120  sieve  :  — 

Table  No.   2. 

0  per  cent,  retained  by  No.  120  sieve  —  W't  per  cubic  foot 
10       "  "  "  "  "  " 

20       "  "  "  «'  "  '< 

30       "  "  "  "  "  " 

4Q  (<  a  a  a  ii  (< 

It  was  soon  discovered  that  there  was  no  direct  ratio  between: 
weight  and  strength.  As  a  general  rule,  subject  to  exceptions, 
heavy  cement,  if  thoroughly  burned  and  fine-ground,  was  preferred 
to  light  cement.  Fine-ground  cements  were  lighter  than  coarse- 
ground  and  underburned  rock  lighter  than  well-burned.  While  color- 
and  weight  by  themselves  indicated  little,  yet,  considered  together- 
and  also  in  connection  with  fineness,  they  enabled  the  inspector  to 
guess  at  the  character  of  a  cement,  and  suggested  reasons  for  high 
or  low  breaking.  A  cement  which  was  light  in  color  and  weighty, 
and  also  coarse-ground,  would  be  viewed  with  suspicion. 

The  test  of  fineness,  which  followed,  was  considered  of  great 
importance,  as  showing  the  quantity  of  actual  cement  contained  in  a 
barrel,  and   its   consequent  value.      Small  scales  were  used,  made 


.  .  75 

pounds. 

.  .  79 

(< 

.   .  82 

(1 

.  .  86 

(( 

.  .  90 

(C 

116  MAIN    DRAINAGE    WORKS. 

for  this  purpose  by  Fairbanks  &  Co.  One-quarter  of  a  pound  of 
the  sample  was  weighed  out  and  passed  through  the  sieve.  The 
coarse  particles  retained  by  the  sieve  were  returned  to  the  scales, 
whose  balance-beam  carried  a  movable  weight,  and  was  graduated 
in  percentages  of  one-quarter  pound.  The  percentage  of  coarse 
particles  retained  by  the  sieve  could  thus  be  read  directly  from  the 
beam. 

Standard  sieves,  varying  from  No.  50  to  No.  120,  were  used.  The 
number  of  meshes  to  the  lineal  inch  in  any  sieve  is  commonly  sup- 
posed to  correspond  with  its  trade  number.  As  sold,  however,  they 
vary  somewhat,  and  the  number  of  wires  is  generally  less,  by  about 
ten  per  cent.,  than  the  number  of  the  sieve.  A  No.  50  sieve  com- 
monly has  about  45  meshes  to  the  inch,  and  a  No.  1'20  about  100,  or 
a  few  more.  In  important  contracts,  where  a  certain  degree  of  fine- 
ness was  called  for,  it  was  customary  carefully  to  compare  two  sieves 
and  retain  one,  which  was  specified  as  the  standard,  while  the  other 
was  delivered  to  the  manufacturer  for  his  guidance. 

In  accordance  with  common  practice  the  No.  50  sieve  was  first 
used.  It  was  soon  discovered,  however,  that  so  coarse  a  sieve  did 
not  always  give  a  correct  indication  of  the  fineness  of  the  cement. 
This  was  especially  true  of  Portland  cements.  Some  brands,  chiefly 
German,  were  evidently  bolted  by  the  manufacturers  with  special 
reference  to  tests  by  this  sieve,  in  which  they  would  leave  no  re- 
siduum. Yet  the  bulk  of  such  cements,  while  containing  no  very 
coarse  particles,  might  prove  quite  coarse  when  tested  by  the  No. 
120  sieve. 

It  is  obvious  that  pieces  of  burned  cement  slag  one-fourth  of  an 
inch  in  diameter  would  have  no  cementing  quality,  and  the  same  is 
true  of  particles  one  one-hundredth  of  an  inch  in  diameter.  At 
precisely  what  smaller  size  the  particles  begin  to  act  as  cement  it  was 
impossible  to  determine.  Those  retained  by  a  No.  120  sieve,  in 
which  the  open  meshes  are  approximately  one  two-hundredth  of  an 
inch  square,  were  found  to  have  some  slight  coherence,  even  after 
washing  to  remove  the  finer  floury  cement  which  was  sticking  to  them. 
It  was  also  found  that  the  No.  120  sieve  was  about  as  fine  a  one  as  it 
was  practicable  to  use,  on  account  of  the  time  required  to  sift  the 
cemeiit  through  it.    It  was,  therefore,  adopted  as  a  standard. 

Assuming  (what  was  only  approximately  verified  by  experiments 
on  tensile  strength)  that  only  what  passed  through  this  sieve  had  real 
value  as  cement,  and  that  the  rest  was  not  very  different  from  good, 
sharp  sand,  the  difference  in  the  quantity  of  actual  cement  obtained 
in  purchasing  barrels  60  and  90  per  cent,  fine,  respectively,  is  shown 


APPENDIX    A.  117 

by  Figs.  9  and  10,  Plate  XXVIII.  This  has  an  important  bearing 
on  the  proportion  of  sand  to  be  added  in  practical  use  ;  for  when 
mortar  is  mixed  for  use  in  the  proportion  of  one  barrel  of  cement 
to  two  of  sand,  if  there  be  nine  parts  of  cement  and  one  of  sand  in 
the  barrel  of  cement  itself,  the  actual  proportion  in  the  mortar  will 
be  .9  to  2.1  or  1  to  2.33.  If  there  be  only  six  parts  of  cement  and 
four  of  sand  in  the  barrel  of  cement  the  resulting  proportion  in  the 
mixture  will  be  ,6  to  2.4  or  1  to  4. 

Fine  cement  can  be  produced  by  the  manufacturers  in  three  ways  : 
by  supplying  the  mill-stones  with  comparatively  soft,  underburnt 
rock,  which  is  easily  reduced  to  powder  ;  by  running  the  stones  more 
slowly,  so  that  the  rock  remains  longer  between  them ;  or  by  bolting 
through  a  sieve  and  returning  the  unground  particles  to  the  stones. 
The  first  process  produces  an  inferior  quality  of  cement,  while  the 
second  and  third  add  to  the  cost  of  manufacturing. 

The  extra  cost,  as  estimated  by  a  firm  of  English  manufacturers,  of 
reducing  a  Portland  cement  from  an  average  of  70  per  cent,  fine, 
tested  by  No.  120  sieve,  to  90  per  cent,  fine,  was  18  cents  per  barrel. 
The  price  at  which  5,000  barrels  of  their  ordinary  make,  70  per  cent, 
fine,  were  offered,  delivered  on  our  work,  was  S2.82  per  barrel.  The 
same  cement,  ground  88  per  cent,  fine,  was  delivered  for  S3  a  barrel. 
On  the  foregoing  assumption  of  the  value  of  fine  and  coarse  particles, 
the  city,  by  accepting  the  first  offer,  would  have  obtained  in  bulk 
3,500  barrels  of  actual  cement  and  1,500  barrels  of  sand  for  $14,100. 
By  accepting  the  second  off'er  it  obtained  in  bulk  4,400  barrels  of 
cement  and  600  of  sand  for  $15,000;  that  is,  the  900  additional 
barrels  of  cement  cost  $1  a  barrel.  Experiments  illustrating  the  value 
of  fine  grinding,  and  further  comments,  will  be  given  later. 

Tests  were  made  both  of  neat  cement  and  of  cement  mixed  with 
sand  in  different  proportions.  The  latter  were  preferred,  because  they 
showed  the  strength  and  value  of  the  mortars  used  in  actual  work.  It 
was  found  also  that  the  strength  of  briquettes  made  of  neat  cements 
did  not  always  indicate  the  capacity  of  these  cements  to  bind  sand, 
or  the  strength  of  the  mortars  made  with  them.  This  is  illustrated 
by  experiment  No.  10,  on  page  127. 

The  greater  the  proportion  of  sand  in  the  mortar  tested  the  more 
accurately  was  the  actual  cementing  quality  of  the  cement  indicated. 
As,  however,  very  weak  mixtures  took  a  long  time  to  harden,  and  were 
liable  to  injury  from  handling,  one  part  cement  to  three  parts  sand 
was  adopted  as  the  usual  mixture  for  testing  Portland  cements,  and 
one  to  one  and  one-half  or  two  for  American  cements.  Occasionally 
when  testing  large  quantities  of  some  well-known  brand,  the  object 


118  MAIN    DRAINAGE    WORKS. 

being  to  see  that  a  UDiform  strengtli  was  maintained,  it  was  found 
sufficient,  and  simpler,  to  omit  the  sand  and  make  the  briquettes 
of  cement  only. 

In  making  mortars  for  testing,  rather  coarse,  clean,  sea-beach  sand 
was  used. 

The  subsequent  strength  of  the  briquettes  depended  largely  upon 
the  amount  of  water  with  which  they  were  gauged.  The  highest  re- 
sults were  obtained  by  using  just  enough  water  thoroughly  to  dampen 
the  cement,  giving  the  mass  the  consistency  of  fresh  loam,  which  be- 
came pasty  b}'  working  with  a  trowel.  For  ordinary  testing,  sufficient 
water  was  added  to  make  a  plastic  mortar,  somewhat  stiff er  than 
is  commonly  used  by  masons.  Different  ■  cements  varied  in  the 
amounts  of  water  needed  to  produce  this  result.  As  a  rule  American 
cements  needed  more  water  than  Portland,  fine  ground  more  than 
coarse,  and  quick-setting  more  than  more  slow-setting  cements. 
Experiment  No.  9,  page  127,  shows  the  comparative  strength  of  mor- 
tars gauged  with  different  percentages  (in  weight  of  the  cement)  of 
water.  The  standard  adopted  was  25  per  cent,  for  Portland  cement 
and  33  per  cent,  for  Rosendale  ;  but  these  amounts  were  increased  or 
diminished  by  the  operator  to  suit  the  circumstances,  his  aim  being  to 
obtain  mortars  of  unvarying  consistency. 

The  way  in  which  the  test  briquettes  were  made  was  as  follows  : 
the  moulds,  having  been  slightly  greased  inside  to  prevent  the  mor- 
tar sticking  to  them,  were  placed  on  a  polished  marble  slab.  This 
support  for  them  was  used  because  it  was  easily  cleaned  and  the  mor- 
tar did  not  stick  to  it.  Experiment  No.  6,  page  124,  shows  that  the 
use  of  porous  or  of  non-porous  beds  to  support  the  moulds  does  not 
materially  affect  the  strength  of  the  mortars.  The  requisite  amounts  of 
cement  and  sand  for  one  briquette  were  weighed  out  and  incorporated 
dry  in  a  mixing-pan.  The  proper  amount  of  water  was  also  weighed 
out  and  added,  and  the  mass  worked  briskly  with  a  small  trowel  until 
of  uniform  consistency.  A  brass  mould  was  half  filled  with  the  mor- 
tar, which  was  rammed  into  place  by  the  operator  with  a  small  wooden 
rammer,  in  order  to  displace  any  bubbles  of  air  which  might  be  con- 
fined in  it.  The  mould  was  then  filled  to  its  top  with  the  remaining 
mortar,  which  was  in  turn  rammed  down.  Finally  the  mortar  was 
struck  even  with  the  top  of  the  mould  and  given  a  smooth  surface 
by  the  trowel. 

The  amount  of  mortar  packed  in  the  mould,  and  the  consequent 
density  of  the  briquette,  would  vary  with  any  variation  in  the  degree 
of  force  exerted  by  the  operator  in  ramming.  This  variation  was  re- 
duced to  a  minimum  by  always  mixing  a  fixed  amount  of  mortar, 


APPENDIX    A.  119 

which  was  barely  more  than  sufficient  to  fill  one  mould.  Irregularities 
in  ramming  would  thus  be  detected  by  variations  in  the  amount  of 
surplus  mortar,  and  could  be  checked.  An  attempt  was  made  to  do 
away  wholly  with  this  element  of  uncertaint}^  by  pressing  the  mortar 
into  the  moulds  with  certain  fixed  pressures.  Apparatus  was  devised 
and  used  for  this  purpose,  but  was  finally  abandoned  on  account  of 
the  length  of  time  required  for  its  use. 

The  initial  energy  of  the  cement —  that  is,  the  length  of  time  after 
mixing  before  it  "  set  "  —  was  determined  by  noting  the  length  of 
time  before  it  would  bear  "the  light  wire"  of  -^-^  inch  in  diameter 
loaded  with  J-pound  weight,  and  also  "the  heavy  wire"  2'^  inch  in 
diameter  loaded  with  1-pound  weight.  At  the  former  time  tlie  cement 
was  said  to  have  begun  to  set,  and  at  the  latter  it  was  entirely  set. 
DilJerent  kinds  and  brands  of  cement  varied  greatly  in  the  time  after 
mixing  when  they  would  bear  the  wires.  Some  brands  of  English 
Roman  cement  would  set  in  two  minutes,  and  some  of  Portland  re- 
quired over  12  hours.  Cold  retarded  the  setting,  and  fresh-ground 
cements  set  quicker  than  older  ones.  No  direct  relation  was  estab- 
lished between  initial  energy  and  subsequent  strength.  Bj^  judicious 
mixing  of  quick  and  slow  setting  cements  a  mixture  could  be  ob- 
tained which  would  set  within  any  desired  period. 

As  soon  as  the  briquettes  were  hard  enough  to  handle  without  injury, 
which  with  different  cements  and  mixtures  varied  from  five  minutes  to 
twelve  or  more  hours,  they  were  removed  from  the  moulds  and  placed 
in  numbered  pans  filled  with  water.  Before  removal  each  briquette 
had  marked  upon  it,,  with  steel  stamps,  the  name  of  the  cement,  date 
of  mixing,  and  a  number  by  which  it  could  be  further  identified.  The 
inscription  might  read  thus  :  — 

"Alsenl-3.     May  17,  1880.     47." 

Records  were  also  kept  in  books  and  on  blanks  provided  for  the 
purpose.  The  briquettes  were  kept  in  the  pans,  covered  with  water, 
until  they  were  broken.  Their  age  when  broken  varied  from  24  hours 
to  five  years. 

In  testing  a  well-known  American  cement,  of  generally  uniform 
quality,  if  it  were  an  object  to  save  time,  the  comparative  excellence 
of  the  samples  could  be  sufBciently  determined  by  a  24  hours'  test  of 
briquettes  made  of  neat  cement.  Under  similar  conditions  neat  Port- 
land cement  could  be  tested  in  seven  days.  To  test  mortar  of  either 
kind  of  cement  took  a  week,  or,  better,  a  month  ;  especially  if  there 
was  a  liberal  proportion  of  sand. 

The  probable  value  of  an  untried  brand  of  cement  could  hardly 


120  MAIN    DRAINAGE    WORKS. 

be  ascertained  with  certainty  in  less  than  a  month,  and  not  always 
then.  To  illustrate  the  occasional  need  of  long-time  tests  a  case  may 
be  cited. 

A  new  brand  of  cement,  made  by  some  patent  process,  was  offered 
for  use  on  the  work.  When  tested  it  set  up  well,  and  at  the  end 
of  a  week  the  neat  cement  had  a  tensile  strength  of  184  pounds  per 
square  inch.  In  a  month  this  had  increased  to  267  pounds,  indicating 
a  strength  equal  to  that  of  a  low-grade  Portland  cement.  At  this 
time  there  was  nothing  in  the  appearance  of  the  briquettes  to  indicate 
any  weakness.  Yet  after  about  six  months  they  fell  to  pieces,  and  had 
entirely  lost  their  cohesive  quality. 

The  briquettes  were  broken  by  a  machine  made  for  the  Department 
by  Fairbanks  &  Co.  It  worked  with  levers,  acting  on  a  spring  bal- 
ance, which  was  tested  from  time  to  time,  and  found  to  maintain  its 
accuracy. 

During  the  progress  of  the  work  the  following  brands  of  cement 
were  submitted  for  approval,  and  were  tested  with  more  or  less  thor- 
oughness :  — 

Old  Newark,  Newark  and  Rosendale,  Norton,  Hoffman,  OldEosen- 
dale,  New  York  and  Rosendale,  Lawrenceville,  Rosendale,  Arrow, 
Keator,  Howe's  Cave,  Rock  Lock,  Buffalo,  Cumberland,  Round  Top, 
Selenitic,  Vorwholer,  Star,  Dyckerhoff,  Alsen,  Hemmor,  Bonnar, 
Onward,  Burham,  J.  B.  White,  Knight,  Bevan  &  Sturge,  Brooks, 
Shoobridge  &  Co.,  Leavitt,  Grand  Float,  Diamond,  Spanish,  Red 
Cross,  La  Farge,  Lime  of  Teil,  S.aylor,  Coolidge,  Walkill,  Cobb, 
Abbott. 

The  following  is  a  record  of  the  more  instructive  tests,  made  for 
experimental  purposes.  Nearly  all  of  them  were  made  with  special 
reference  to  the  work  then  in  hand,  to  elucidate  some  practical  ques- 
tions affecting  the  purchase,  testing,  or  use  of  the  cements  needed  for 
building  purposes.  The  names  of  the  brands  of  cement  tested  in  the 
several  experiments  are  generally  omitted.  This  is  in  order  to  avoid 
any  unwarranted  use  of  the  results  as  recorded. 

The  figures  given  in  the  tables  always  represent  average  breaking 
loads  in  pounds  per  square  inch  of  breaking  section. 

Experiment  No.   1. 

Of  natural  American  cements  the  Rosendale  brands  (so  called)  are 
the  only  ones  which  find  a  sale  in  the  Boston  market,  and  they  were 
chiefly  used  on  the  work.  Imported  Portland  cements  were  also 
largely  used.     It  was  important,  therefore,  to  ascertain  the  actuai  and 


APPENDIX    A. 


121 


comparative  strengths  of  these  cements.  The  following  table  gives 
results  compiled  from  about  25,000  breakings,  of  20  different  brands, 
and  fairly  represents  the  average  strength  of  ordinary  good  cements 
of  the  two  kinds.  Some  caution,  however,  is  necessary  in  using  the 
table  as  a  standard  with  which  to  compare  other  cements.  Quick- 
setting  cements  might  be  stronger  in  a  day  or  week,  and  show  less 
increase  in  strength  with  time.  Fine-ground  cements  would  probably 
give  lower  results  tested  neat,  and  higher  ones  with  liberal  propor- 
tions of  sand. 


Table  No.  3. 

EOSENDALE    CEMENT. 


Neat  Cement. 

Cement,  1; 
Sand,  1, 

Cement,  1 ; 
Sand,  1.5. 

Cement,  1 ; 
Sand,  2. 

Cement,  1; 
Sand,  3. 

Cement,  1 ; 
Sand,  5. 

c 

71 

92 

6 
145 

o 
to 

282 

o 

:^ 

290 

56 

6 
116 

o 
to 

190 

o 
256 

41 

o 

to 

155 

o 

:^ 

230 

24 

d 
60 

o 
to 

125 

o 
180 

6 
35 

o 

a 

to 
80 

o 
121 

5 

d 

I-t 

16 

o 
to 

46 

o 

a 

SO 

Neat  Cement. 

Cement,  1; 
Sand,  1. 

Cement,  1; 
Sand,  1.5. 

Cement,  1; 
Band,  2. 

Cement,  1 ; 
Sand,  3. 

Cement,  1; 
Sand,  5. 

ft 

303 

d 
412 

o 
to 

468 

o 
494 

160 

1 
225 

o 
to 

347 

o 

1— i 

387 

^ 
^ 

6 

o 

o 

126 

d 

rH 

163 

o 
to 

279 

o 
e-i 

323 

95 

d 
140 

o 
198 

o 

rH 

257 

55 

d 
88 

o 

to 

136 

o 
155 

The  table  is  instructive  in  several  ways.  It  shows  that  Portland 
cement  acquires  its  strength  more  quickly  than  Rosendale  ;  that  both 
cements  (but  especially  Rosendale)  harden  more  and  more  slowly  as 
the  proportion  of  sand  mixed  with  them  is  increased  ;  that,  whereas 
neat  cements  and  rich  mortars  attain  nearly  their  ultimate  strength  in 
six  months  or  less,  weak  mortars  continue  to  harden  for  a  year  or  more. 
The  table  shows  the  advantage  of  waiting  as  long  as  possible  before 
loading  masonry  structures,  and  the  possibility  of  saving  cost  by  using 
less  cement  when  it  can  have  ample  time  to  harden.  It  also  shows 
that  Portland  cement  is  especiallj'  useful  when  heavj^  strains  must  be 
withstood  within  a  week. 


122 


MAIN   DRAINAGE    WORKS. 


Experiment  No.  2.  " 

These  series  of  tests  are  like  the  preceding  ones,  except  that  a 
single  brand  of  cement  was  used  in  making  each.  The  average 
breaking  loads  per  square  inch  were  obtained  from  a  less  number  of 
briquettes  (about  500  in  all),  mortars  with  larger  proportions  of  sand 
were  included  in  the  series,  and  the  tests  were  extended  for  two  years. 

Table  No.  4. 

PORTLAND  CEMENT  MORTAR. 


Age  when 

Neat 

Cement,  1 ; 

Cement,  ]  ; 

Cement,!  ; 

Cement,!; 

Cement,!; 

Cement,!; 

Broken. 

Cement. 

Sand,  2. 

Sand,  4. 

Sand,  6. 

Sand,  8. 

Sand,  10. 

Sand,  12. 

One  week 

295 

166 

89 

50 

33 

23 

17 

One  month    . 

341 

243 

132 

88 

67 

50 

41 

Six  months    . 

374 

343 

213 

149 

98 

76 

51 

Two  years     . 

472 

389 

226 

159 

98 

49 

31 

KOSENDALE  CEMENT  MORTAR. 


Age  when 
Broken. 

Neat 
Cement. 

Cement,!; 
Sand,  2. 

Cement,!; 
Sand,  4. 

Cement,  1 ; 
Sand,  6. 

Cement,!; 
Sand,  8. 

Cement,  1 ; 
Sand,  10. 

Cement, ! ; 
Sand,  12. 

.      .      . 

24 

83 

172 

211 

7 
33 
93 
90 

5 

One  month   . 
Six  months    . 
Two  years     . 

17 

62 
56 

8 
50 
33 

5 
33 

22 

21 
20 

The  tables  show  that  considerable  strength  is  acquired  in  time,  even 
when  a  very  large  proportion  of  sand  is  used  ;  also,  that  most  mortars 
increase  very  little,  if  any,  in  tensile  strength  after  six  months  or  a 
year.  They  become  harder  with  time,  but  also  become  more  brittle 
and  probably  less  tough.  Specimens  of  mortar  two  years  old,  or  more, 
break  very  irregularly. 

Experiment  No.  3. 

The  rate  at  which  Rosendale  and  Portland  cements,  respectively, 
increase  in  strength  during  the  first  two  months  after  mixing  is  very 
different,  and  has  some  bearing  on  their  use,  and  more  on  the  inter- 
pretation of  tests  of  them  made  within  that  period.    The  curves  (Fig. 


Plate  XXIX. 


500 


400 


300 


pORTLAmSmMKL 


200 


KX) 


4O0 


300 


20O 


100 


CO 


14  SO 

AGE  IN  DAYS  WHEN  BROKEN. 
FfGJ. 


F/G.2. 

K/ND  or  SAND  USED. 


sandTsT^ 


APPENDIX   A.  123 

1,  Plate  XXIX),  which  indicate  this  rate  of  increase,  were  compiled 
from  tests  with  neat  cement.  It  is  probable  that  tests  with  mortar 
would  give  somewhat  similar  results.  By  comparing  the  two  curves  it 
appeai-s  that  after  24  hours  Rosendale  cement  has  about  three-fourths 
of  the  strength  of  Portland.  While  the  latter  increases  greatly  in 
hardness  during  the  next  few  days,  the  energy  of  the  former  becomes 
dormant,  so  that  at  the  end  of  a  week  the  Portland  cement  is  more 
than  three  times  as  strong  as  the  Kosendale.  During  the  second 
week  the  Portland  cement  increases  more  slowl3-,  and  the  Rosen- 
dale  continues  nearly  quiescent.  At  about  this  period,  and  for  the 
next  six  weeks,  the  Rosendale  cement  gains  strength,  not  only  rela-, 
tively,  but  actually  faster  than  the  Portland,  so  that  when  two  months 
old  the  former  has  one-half  the  strength  of  the  latter.  After  two 
months  the  relative  rate  of  increase  and  the  comparative  strength 
of  the  two  cements  remain  nearly  unchanged.  A  series  of  tests  with 
a  Buffalo  cement,  and  one  with  a  Cumberland  cement,  gave  results 
similar  to  those  with  Roseudale  cement. 

EXPERIMEKT   No.  4. 

For  making  tests  it  is  not  always  convenient  to  obtain  sand  of  uni- 
form size,  and  still  less  so  to  obtain  such  sand  in  sufllcieut  quantities 
for  use  in  work.  The  curves.  Fig.  2,  Plate  XXIX,  record  some  tests 
made  to  determine  the  effect  of  fineness  and  of  uniformity  of  size 
in  sand  upon  the  strength  of  mortars  made  with  it. 

The  curves  show  that  for  comparative  tests  it  is  advisable  to  have 
sifted  sand  of  nearly  uniform  size  ;  that  mortars  made  with  coarse 
sand  are  the  strongest,  and  that  the  finer  the  sand  the  less  the 
strength.  It  also  appears  that  mixed  sand,  i.e.,  unsifted  sand  con- 
taining a  mixture  of  particles  from  coarse  to  fine,  makes  nearly  as 
strong  a  mortar  as  coarse  or  medium  coarse  sand.  For  use  in  work, 
therefore,  it  is  well  to  avoid  fine  sands  ;  but  it  is  not  necessary  to 
have  sand  of  uniform  size,  or  to  sift  out  a  moderate  proportion  of 
fine  particles.  ,, 

Experiment  No.  5. 

As  some  experimenters  on  cement  use  a  test  briquette  with  a  break- 
ing section  of  1  square  inch,  and  others  one  with  a  section  of  2J 
square  inches,  the  following  experiment  was  made  to  determine  the 
difference,  if  any,  in  the  strength  acquired  by  the  same  mortars 
moulded  into  briquettes  of  these  different  sizes.  Two  series  of  tests 
were  made,  in  the  same  way,  with  the  same  mortars.  In  one  series 
the  briquettes  had  a  breaking  section  of  1  square  inch,  and  in  the 


124 


MAIN    DRAINAGE    WORKS. 


other  the  section  was  2^  square  inches.  The  results  are  given  in  the 
following  table,  in  which  the  iigures  represent  breaking  loads  in 
pounds  per  square  inch,  and  are  averages  from  five  breakings  :  — 

Table  No.  5. 


ROSENDALB   CeMENT. 

Portland 

Cement. 

Cement,  1 ; 

Neat 

Cement,  ]  ; 

Neat  Cement. 

Sand,  1.5. 

Cement. 

Sand,  1.5. 

^ 

.a 

J2 

^ 

_^ 

1 
1 

M 

^ 

J 

M 

^ 

•3 

>> 

^ 

a 
o 

o 

o 

d 
o 

ri 
o 

o 

1 

o 

o 

3 

!H 

iH 

'"' 

CD 

1-1 

'"' 

«■ 

i-i 

r-l 

o 

iH 

tH 

to 

1-inch  Section    .     .     . 

49 

73 

156 

286 

27 

53 

236 

309 

460 

657 

60 

96 

175 

2^-inch  Section  .     .     . 

49 

78 

173 

258 

27 

62 

311 

347 

391 

578 

67 

108 

230 

As  is  usual,  the  breaking  loads  are  somewhat  irregular,  the  inch 
section  excelling  at  some  points,  and  the  larger  section  at  others. 
The  experiment,  however,  seems  to  indicate  that  neither  size  will,  as 
a  rule,  give  higher  results  than  the  other. 

Expp:riment  No.  6. 

Some  experimenters  have  thought  it  important  to  place  the  moulds 
ill  which  the  mortar  is  packed  for  testing  upon  a  porous  bed,  such  as 
blotting-paper  or  plaster.  Others  use  a  non-porous  bed  of  glass,  slate, 
or  marble.  The  following  series  of  tests  were  made  to  discover  the 
effect  of  these  different  modes  of  treatment.  The  figures  in  the 
tables  represent  breaking  loads,  in  pounds  per  square  inch,  and  are 
averages  of  about  ten  breakino-s. 


Table  No.  6. 

KOSENDALE    CEMENT. 

Mixture. 

Kind  of  Bed. 

One  Week. 

One  Month. 

Six  Months. 

One  Year. 

Neat      .     1 

Marble  .     . 
Plaster  .     . 

95 
106 

151 

178 

288 
303 

825 
316 

Cement,  1, 
Sand,    1.6. 

Marble  .     . 
Plaster  .     . 

44 
62 

107 
120 

210 
219 

251 
265 

APPENDIX    A. 


125 


A    CTJBIBERLAND    CEMENT. 


Mixture. 

Kind  of  Bed. 

One 
Day. 

One 
Week. 

One 
Month. 

Six 
Months. 

One 
Tear. 

Neat    .     .          < 

Marble    .  '  .     . 
Plaster    .     .     . 

128 
147 

133 
165 

142 
176 

231 
244 

241 
257 

Marble    . 

107 
128 

161 
166 

275 
299 

339 

Sand    1.5      .     . 

Plaster    .     .     . 

345 

Cement,  1 

Marble    . 

85 
111 

134 
148 

201 
241 

292 

Sand,  2    .     .     . 

Plaster    . 

294 

Cement,  1 

Marble    . 

40 
46 

94 
91 

162 
164 

163 

170 

GERMAN    PORTLAND    CEMENT. 


Mixture. 

Kind  of  Bed. 

One  Weels. 

One  Month. 

Six  Months. 

One  Tear. 

Cement,  1, 
Sand,   1     . 

Marble  .     . 
Plaster  .     . 

259 
213 

367 
376 

390 
411 

.      . 

Cement,  1, 
Sand,  2     . 

Marble  .     . 
Plaster  .     . 

176 
196 

256 

258 

346 
326 

345 
357 

Cement,  1, 
Sand,  3     . 

Marble  .     . 
Plaster  .     . 

141 
147 

225 
220 

250 
258 

313 
312 

Cement,  1, 
Sand,  4     . 

Marble  .     . 
Plaster  .     . 

103 
120 

157 
150 

240 
233 

274 
264 

Cement,  1, 
Sand,  5     . 

Marble  .     . 
Plaster  . 

82 
103 

108 
140 

182 
193 

213 
197 

Making  allowance  for  a  few  irregularities,  it  appears,  from  the  fore- 
going tables,  that  the  use  of  a  porous  bed  gives  slightly  higher 
results  for  the  first  one  or  two  mouths,  but  that  the  difference  disap- 
pears or  becomes  insignificant  with  age. 


126 


MAIN    DRAINAGE    WORKS. 


Experiment  No.  7. 

It  is  a  well-recognized  fact  that  iu  experimenting  with  cements,  even 
when  great  care  is  exercised,  individual  specimens  break  very  irregu- 
larl}',  and  that  results  even  approximately  conforming  to  theory  can 
only  be  obtained  from  averages  from  a  large  number  of  breakings. 
The  personal  equation  of  the  operator,  and  the  degree  of  force  with 
which  he  presses  the  mortar  into  the  moulds,  is  one  factor  in  pro- 
ducing irregular  results.  To  do  away  with  this  a  machine  for  i)acking 
the  moulds  was  devised  and  used  for  a  time.  By  this  the  mortar  was 
pressed  into  the  moulds  by  a  metallic  plunger,  acting  with  definite 
pressures,  varying  from  50  to  400  pounds. 

The  macliine-raade  briquettes  broke  with  somewhat  greater  uni- 
formity than  hand-made  ones.  So  much  more  time  was  required  to 
make  briquettes  with  this  machine  that  it  was  found  to  be  impracti- 
cable to  employ  it  for  general  use. 

Experiment  No.  8. 

By  the  sea  it  is  frequently  convenient  to  mix  mortar  with  salt  water. 
Brine  is  also  used  in  winter  as  a  precaution  against  frost.  This 
experiment  was  made  to  obtain  the  comparative  effect  of  mixing 
with,  and  immersing  in,  fresh  and  sea  water  respectively.  The  tests 
were  made  upon  a  Rosendale  mortar,  mixed  one  part  cement  to  one 
part  sand,  and  an  English  Portland  mortar,  one  part  cement  to  two 
parts  sand.  The  figures  are  averages  of  about  ten  breakings,  and 
give  the  tensile  strength  in  pound  per  square  inch  with  the  different 
methods  of  treatment  and  at  different  ages. 

Except  for  some  irregularity  in  the  breakings  for  one  year  (which 
may  have  been  due  to  the  manipulation)  the  table  indicates  that 
salt,  either  in  the  water  used  for  mixing  or  that  of  immersion,  has  no 
important  effect  upon  the  strength  of  cement.  Salt  water  retards  the 
first  set  of  cement  somewhat. 

Table  No.   7. 


ROSBNDALB  CBMENT  MoBTAE. 
1  TO  1. 

Portland  Cement  Mortar, 

1  TO  2. 

Fresh  Water. 

Fresh. 

Salt. 

Salt. 

Mixed  with 

Fresh. 

Fresh. 

Salt. 

Salt. 

Fresh  Water. 

Salt. 

Fresh. 

Salt. 

Immersed  in 

Fresh. 

Salt. 

Fresh. 

Salt. 

40 
126 
247 
310 

48 
185 
250 
263 

60 
114 
243 
224 

61 
126 
224 
217 

One  week.  . 
One  month. 
Six  months. 
One  year.    . 

151 
213 
314 
342 

122 
191 
245 
231 

152 
203 

277 
346 

149 
200 
264 
295 

Plate   XXX. 


15  .20  25  30  35  40  45  50 

PER  CENT  or  WA  TER  Or  MfXTURE  fN  WC/GHT  OF  CEMENT. 


APPENDIX    A. 


127 


Experiment  No.  9. 

This  was  an  experiment  to  determine  the  relation  existing  between 
the  stiffness  of  cement  mortar  when  first  mixed  and  its  subsequent 
strength.  The  stiffness  depends  on  the  proportion  of  water  used  in 
mixing,  and  varies  somewhat  with  different  cements.  Natural  Ameri- 
can cements  take  up  more  water  than  Portland  cements  and  fine- 
ground  more  than  coarse  cements.  Many  series  of  tests  bearing  on 
this  point  were  made.  The  results  obtained  from  two  of  the  more 
complete  series  are  shown  b}'  the  curves  on  Plate  XXX.  The  cements 
used  in  these  tests  were  a  rather  coarse  English  Portland  and  a  fair 
Rosendale.  Each  of  the  points  in  the  curves  represents  an  average 
from  about  ten  briquettes.  The  cements  were  tested  neat,  and  the 
amounts  of  water  used  were  different  percentages,  by  weight,  of  the 
amounts  of  cement.  The  resulting  stift"ness  of  mortar  is  indicated  on 
the  curves.  This  varied  from  the  consistency  of  fresh  loam  to  a  fluid 
grout.    The  time  of  setting  is  greatly  retarded  by  the  addition  of  water. 

The  curves  show  that  from  20  to  25  per  cent,  of  water  gives  the 
best  results  with  Portland  cement,  and  from  30  to  35  per  cent,  with 
Rosendale  ;  that  the  differences  in  strength  due  to  the  amount  of  water 
are  considerable  at  first,  but  diminish  greatly  with  age  ;  that  the  soft 
mortars,  even  when  semi-fluid,  like  grout,  attain  considerable  strength 
in  time. 

Experiment  No.  10. 
From  the  first  it  was  observed  that,  fine-ground  cements  were  less 
strong  when  tested  neat,  and  stronger  when  mixed  with  sand,  than  were 
coarse  cements.  A  few  examples  of  this  are  given  below.  In  the  first 
table  a  coarse  English  Portland  cement  is  compared  with  a  fine-ground 
French  Portland.  The  per  cent,  of  each  retained  by  the  fine  No.  120 
sieve  is  given,  and  the  tensile  strength,  in  pounds,  per  square  inch  at 
the  end  of  seven  days. 

Table  No.  8. 


Kind  of  Cement. 

Per  Cent. 

retained  by 

No.  120  Sieve. 

Parts  of  Sand  to  1  part  of 
Cement. 

0 

2 

3 

4 

5 

English  Portland     .... 

37 

319 

125 

89 

59 

43 

French  Portland     .... 

13 

318 

205 

130 

114 

86 

128 


MAIN   DRAINAGE    WOBKS. 


Such  examples  could  be  multiplied.  German  Portland  cements 
were  commonly  finer  ground  than  English,  and,  as  a  rule,  were  no 
stronger,  or  less  strong,  tested  neat,  but  were  much  stronger  with  lib- 
eral proportions  of  sand.  In  the  following  table  two  lots  of  the  same 
brand  of  English  Portland  cement  are  compared.  The  coarse  cement 
was  the  ordinary  make  of  the  manufacturers  ;  the  fine  cement  differed 
in  no  particular  from  the  other  except  that  it  was  ground  more  slowly 
and  finer  to  meet  the  requirements  of  a  special  agreement.  The  age  of 
the  samples  wheu  broken  was  28  days. 

Table  No.  9. 


Kind  of  Cement. 

Per  Cent. 

retained  by 

No.  120  Sieve. 

Parts  of  Sand  to  1  part  of 
Cement. 

0 

3 

5 

Ordinary  Cement      .... 

35 

403 

105 

68 

Pine-ground  Cement      .     .     . 

12 

30i 

180 

96 

Different  brands  of  Rosendale  cement  varied  considerably  in  their 
fineness.  Those  of  the  best  reputation  would  leave  from  4  to  10  per 
cent,  residuum  in  the  No.  50  sieve ;  other  brands  would  leave  in  the 
same  sieve  from  10  to  23  per  cent.  In  the  following  table  is  com- 
pared the  average  tensile  strength  obtained  from  experiments  with 
three  of  the  finer-ground  brands,  and  also  with  three  other  brands  of 
good  reputation,  but  more  coarsely  ground.  The  age  of  the  speci- 
mens was  one  week. 

Table  No.  10. 


Kind  of  Cement. 

Per  Cent, 
retained  by 

No.  50  Sieve. 

Parts  of  Sand  to  1 
Cement. 

part  of 

0 

1.5 

2 

Fine  Rosendale 

6 

92 

41 

25 

Coarse  Rosendale      .... 

17 

98 

29 

16 

The  foregoing  experiments  show  that  it  is  impossible,  by  tests  on 
the  tensile  strength  of  neat  cements  alone,  to  judge  of  their  value 


APPENDIX    A. 


129 


in  making  mortars,  for  practical  use  ;  also,  that  iiue-grouud  cements 
make  stronger  mortars  than  do  coarser  ones. 

A  number  of  series  of  tests  were  made  of  cements  which  had  been 
sifted  through  sieves  of  different  degrees  of  fineness,  and  had  thereby 
had  different  percentages  of  coarse  particles  removed  from  them. 
The  results  from  these  experiments  were  quite  uniform,  and  showed 
that,  in  proportion  as  its  coarse  particles  were  removed,  a  cement 
became  more  efficient  for  making  mortars  with  sand.  The  following 
table  gives  the  results  obtained  from  one  such  series  of  tests  made 
with  an  English  Portland  cement.  In  the  experiment  comparison  is 
made  between  the  strength  of  mortars  made  with  the  ordinary  cement, 
unsifted  as  it  came  from  the  barrel,  and  those  made  with  the  same 
cement  after  having  been  sifted  through  Nos.  50,  70,  100,  and  120 
sieves,  which,  respectively,  eliminated  more  and  more  of  the  coarse 
particles.  The  per  cent,  of  particles  which  would  still  be  retained  by 
the  tine  No.  100  sieve,  after  sifting  through  the  coarser  sieves,  is 
given  in  the  second  column  of  the  table.  There  is  included  in  the 
table  an  extra  coarse  cement,  which  was  made  so  by  adding  to  unsifted 
cement  a  certain  amount  of  the  coarse  particles  taken  from  the  sifted 
cements.     The  tensile  strength  is  given  in  pounds  per  square  inch. 

Table  No.   11. 


Ph 

Kind  of  Cement 
used  in  making 

MOBTARS. 

Cement    -with    coarse 
particles  added  .    . 

55 

Ordinary  Cement,  un- 
sifted       

33 

Cement  which  passed 
No.  50  Sieve  .     .     . 

28 

Cement  which  passed 
No.  70  Sieve  .     .     . 

18 

Cement  which  passed 
No.  100  Sieve ,     .     . 

8 

Cement  which  passed 
No.  120  Sieve .     .     . 

0 

One  Week.       One  Month 


Sis  Months. 


One  Teab. 


Parts  of  Sand  to  1  part  of  Cement. 


2345       2345       2345       2345 


92 
165 
170 
193 
215 
218 


130 


MAIN    DRAINAGE    WORKS. 


In  a  similar  series  of  tests  with  Rosendale  cement  mortars,  the 
increase  in  strength  obtained  bj'  substituting  fine  for  coarse  particles 
in  the  cement  was  much  less  marked.  The  coarse  particles  were 
softer  than  those  from  Portland  cement,  and  had,  in  themselves,  some 
power  of  cohesion.  As  previous  tests  had  shown  that  fine-ground 
Rosendale  cements  were  stronger,  with  sand,  than  coarse-ground,  it 
was  assumed  that  the  superiority  was  due,  not  so  much  to  the  absence 
of  palpably  coarse  particles,  as  to  the  fact  that  the  bulk  of  the  cement 
was  more  floury,  and  thus  better  adapted  to  coating  and  binding  the 
particles  of  sand.  Probably  natural  American  cement  is  as  much 
improved  as  is  Portland  cement  by  fine  grinding,  but  in  the  case  of 
the  former  there  would  not  be  the  same  relative  advantage  in  bolting 
out  the  coarse  particles  after  grinding. 

The  following  series  of  tests  may  be  of  interest,  on  account  of  the 
age  of  the  specimens.  The  mortars  were  made  with  an  English 
Portland  cement,  both  unsifted  as  taken  from  the  cask,  and  also 
after  it  had  been  sifted  through  the  No.  120  sieve,  by  which  process 
about  35  per  cent,  of  coarse  particles  was  eliminated. 

Table  No.  12. 


Neat  Cement. 

Cement,  1 ;  Sand,  2. 

Cement,  1 ;  Sand,  5. 

2  Tears. 

4  Tears. 

2  Tears. 

4  Tears. 

2  Tears. 

4  Tears. 

Ordinary  Cement,  un- 
sifted     

Cement  which  passed 
No.  120  Sieve     .     . 

603 
374 

387 
211 

339 

478 

493 
580 

182 
250 

202 
284 

This  table,  also,  shows  that  fine  cements  do  not  give  as  high  re- 
sults tested  neat  as  do  cements  containing  coarse  particles,  even  coarse 
particles  of  sand.  It  also  shows  (what  is  often  noticed)  that  neat 
cements  become  brittle  with  age,  and  are  apt  to  fly  into  pieces  under 
comparatively  light  loads. 

The  series  of  tests  which  follows  was  made  for  the  purpose  of  as- 
certaining what  value,  if  any,  for  cementing  purposes,  was  possessed 
by  the  hard,  coarse  particles  of  Portland  cement.  Mortars  were 
made  with  an  ordinary  English  Portland  cement,  and  compared  with 
similar  mortars  made  with  the  same  cement,  after  sifting  through  the 
No.  120  sieve,  which  retained  33  per  cent,  of  coarse  particles. 


APPENDIX   A. 

Table  No.  13. 


131 


One  Week. 

One  Month. 

Six  Months. 

One  Year. 

Kind  of  Cement. 

Parts  of  Sand  to  one  part  of  Cement. 

0 
353 
311 

2 
139 

187 

3 

86 
132 

0 
279 
243 

2 
201 

275 

3 

142 
201 

0 
438 
268 

2 
323 
367 

3 
253 
310 

0 
444 
306 

2 
343 
434 

3 

Ordinary  Cement,  unsifted    . 

Cement  which  passed  No.  120 
Sieve  

271 
338 

As  usual,  the  coarse  cement  was  stronger  neat,  and  weaker  with 
sand.  Assuming  that  the  33  per  cent,  of  coarse  particles  retained 
by  the  sieve  had  no  value  as  cement,  acting  merely  as  so  much  sand, 
and  assuming  also  that  all  which  passed  through  the  sieve  was  good 
cement,  it  follows  that  the  ordinary  unsifted  cement  with  two  parts  of 
sand,  made  a  mortar  in  which  the  proportion  of  real  cement  to  sand 
was  .67  to  2.33,  or  about  1  to  3.5.  Hence,  the  mortar  made  with 
fine  cement  and  three  parts  of  sand  should  be  as  strong,  or  a  little 
stronger,  than  that  made  with  the  coarse  cement  and  two  parts  of 
sand.  It  will  be  seen  that  the  results  in  the  table  sustain  the  assump- 
tion very  well. 

If,  then,  the  coarse  particles  are  assumed  to  act  merely  as  so 
much  sand,  it  will  not  lessen  the  efficiency  of  the  cement  to  remove 
its  coarse  particles,  and  to  substitute  actual  sand  in  their  place.  This 
was  done  in  making  the  following  series  of  tests.  One  set  of  bri- 
quettes was  made  with  ordinary  cement,  and  another  set  with  the 
same  cement,  from  which  33  per  cent,  of  coarse  particles  had  been 
removed  and  replaced  with  fine  sand. 


Table  No.  14. 


One  Week. 

One  Month. 

Six  Months. 

One  Tear. 

Kind  of  Cement. 

Parts  of  Sand  to  one  part  of  Cement. 

2 

3 

2 

3 

2 

3 

2 

3 

Ordinary  Cement,  unsifted, 

Cement  with  33  per  cent, 
coarse  particles  removed 
and  fine  sand  substituted. 

139 
101 

86 
67 

201 
160 

142 

100 

324 

253 

253 

206 

343 
305 

271 
240 

132 


MAIN    DRAINAGE    WORKS. 


These  briquettes  refused  to  break  in  accordance  with  the  theory, 
and  the  assumed  hj^pothesis  was  not  verified.  It  is  evident  that,  for 
making  mortar,  tlie  coarse  particles  of  Portland  cement  are  superior 
to  ordinary  sand,  but  much  inferior  to  fine  cement.  In  the  mortars 
made  with  the  cement,  in  which  the  coarse  particles  had  been  replaced 
with  fine  sand,  the  real  proportions  of  cement  to  sand  were  1  to  3.5 
and  1  to  5.  It  will  be  noticed  that  the  tensile  strength  was  not  re- 
duced in  like  proportion. 

Experiment  No.   11. 

While  building  masonry  laid  in  American  cement  mortar  it  is  some- 
times desirable  to  increase  the  strength  of  the  mortar  temporarily  or 
in  places.  Rich  Portland  cement  mortars  are  expensive,  and  those 
with  large  proportions  of  sand  are  too  porous  for  many  purposes. 
The  desired  strength  can  be  gained  by  using,  instead  of  the  simple 
American  cement,  the  same  cement  mixed  with  a  percentage  of  strong 
Portland  cement. 

The  following  series  of  tests  was  designed  to  ascertain  the  compara- 
tive strength  of  mortars  made  with  a  Rosendale  cement,  an  English 
Portland  cement,  and  also  a  mixture  composed  of  equal  parts  of 
each :  — 

Table  No.  15. 


Kind  of  Mortar. 

1  Week. 

1  Month. 

6  Months. 

1  Tear. 

Rosendale   Cement,  1 ;  Sand  2     .     . 

Rosendale   Cement,  0.5, ")  o      i    r> 
Portland     Cement,    0.5,  /  '^'^°"'  "    " 

Portland  Cement,  1 ;  Sand,  2  .     .     . 

26 

79 

126 

60 
138 
163 

125 

268 
279 

180 
273 
323 

In  the  foregoing  tests  the  mortar  made  with  mixed  cement  had  an 
unexpected  strength,  approximating  to  that  of  mortar  made  with  pure 
Portland  cement.  In  the  following  series  of  tests  of  mortars  made 
with  lime  of  Teil,  a  fine-ground  French  Portland  cement,  and  the 
lime  and  cement  mixed,  the  strength  of  the  mortar  made  with  the 
mixture  is  almost  exactly  a  mean  between  those  of  the  other  two  mor- 
tars, as  also  the  cost  of  the  mixed  cement  is  a  mean  between  the  costs 
of  the  other  two. 


APPENDIX   A. 


133 


Table  No.  16. 


Kind  of  Mortar. 

1  Week. 

1  Month. 

6  Months. 

1    Tear. 

Lime   of  Teil,  1 ;  Sand,  2     ,     .     .     . 

Lime    of     Teil,     0.5,  \  ^      .    ^ 
Portland  Cement,   0.5,  /  *'^""'  "  '     " 

Portland  Cement,  1 ;  Sand,  2  .     .     . 

40 
100 
170 

65 
135 
265 

150 
255 
350 

195 
■290 
365 

The  best  Portland  cements  sometimes  do  not  set  within  an  hour, 
which  precludes  their  use  for  wet  work.  In  such  cases  quick-setting 
cement  should  be  added  to  them.  Roman  cements  can  be  procured 
which  will  set  in  from  one  to  five  minutes.  Mixtures  of  Roman  and 
Portland  cements  were  often  used  on  the  Main  Drainage  Works.  Such 
mortars  would  set  about  as  quickly  as  if  made  with  Roman  cement 
alone,  and  would  acquire  great  subsequent  strength,  due  to  the  Port- 
land cement  contained  in  them.  This  was  proved  by  many  experi- 
mental tests. 

It  is  probable  that  mixtures  of  any  good  cements  can  be  used  with- 
out risk  ;  but  before  adopting  anj^  novel  combination  it  would  be  wise 
to  test  it  experimentally. 

Experiment  No.  12. 

Engineers  are  accustomed  to  require  that  only  clean  sand  and  water 
shall  be  used  in  making  mortar.  Occasionally  these  requirements 
cause  delay  and  extra  expense.  This  experiment  was  designed  to  as- 
certain how  much  injury  would  be  caused  by  the  use  of  sand  contain- 
ing moderate  proportions  of  loam.  In  mixing  the  mortar  for  these 
briquettes,  sand  containing  10  per  cent,  of  loam  was  used  in  the  place 
of  clean  sand.  Each  figure  in  the  table  is  an  average  (in  pounds  per 
square  inch)  of  ten  breakings. 


Table  No.  17. 

EOSENDALE    CEMENT,     1;    SAND,    1.5;    LOAM,    .15. 


One  "Week. 

One  Month. 

Six  Months. 

One    Tear. 

21 

46 

200 

221 

The  tests  do  not  give  very  decisive  results.     For  one  week  and  one 


134 


MAIN    DRAINAGE    WORKS. 


month  tJie  breaking  loads  are  not  much  more  than  one-half  what 
would  have  been  expected  with  clean  sand.  For  six  months  and  a 
year  they  are  fully  equal  to  ordinary  mortar. 


Experiment  No.  13. 

This  experiment  was  similar  to  the  foregoing  one,  except  that  clay, 
instead  of  loam,  was  added  to  the  mortar.  Clay,  when  dissolved  or 
pulverized,  consists  of  an  almost  impalpable  powder,  with  particles 
fine  enough  to  fill  the  interstitial  spaces  among  the  coarser  particles 
of  cement.  By  adding  cla}'  to  cement  mortar  a  much  more  dense, 
plastic,  and  water-tight  paste  is  produced,  which  was  occasionally 
found  convenient  for  plastering  surfaces  or  stopping  leaky  joints. 
Each  figure  in  the  Portland  cement  series  of  tests  is  an  average  from 
about  fifteen  briquettes  ;  those  in  the  Rosendale  cement  series  are 
averages  from  ten  briquettes. 

Table  No.  18. 

KOSENDALE  CEMENT. 


Cement,  2 ; 
Clay,  1. 

Cement,  1 ; 
Clay,  1. 

Cement,  1 ; 
Sand,  1.5. 

Cement,  1 ; 
Sand,    1.5; 
Clay,  0.15. 

Cement,  1; 
Sand,    1.5; 
Clay,   0.3; 

Cement,  1 ; 
Sand,   1.5; 
Clay,  0.45. 

• 
1  week    .     .     . 

32 

23 

50 

52 

34 

33 

1  month  . 

108 

52 

123 

116 

101 

100 

6  months     .     . 

303 

206 

217 

248 

247 

236 

1  year     .     .     . 

208 

209 

262 

290 

265 

261 

PORTLAND  CEMENT. 


Cement,  2; 
Clay,  1. 

Cement,  1 ; 
Clay,  1. 

Cement,  1 ; 
Sand,  2. 

Cement,  1 ; 
Sand,    2; 
Clay,  0.2. 

Cement,  1 ; 
Sand,    2; 
Clay,  0.4. 

Cement,  1 ; 
Sand,    2; 
Clay,  0.6. 

]  week    .     .     . 

185 

192 

150 

197 

185 

145 

1  month .     .     . 

263 

271 

186 

253 

245 

203 

6  months 

348 

322 

320 

361 

368 

317 

1  year     .     .     . 

303 

301 

340 

367 

401 

384 

The  tests  seem  to   show  that   the  presence   of    clay  in   moderate 
amounts  does  not  weaken  cement  mortars. 


APPENDIX   A.  135 

It  was  feared  that  the  presence  of  clay  in  mortars  exposed  to  the 
weather  might  tend  to  make  them  absorlD  moisture  and  become  disin- 
tegrated. To  ascertain  whether  this  would  be  so,  sets  of  briquettes 
were  made,  one  set  of  Portland  cement  and  sand  only,  the  other  con- 
taining also  different  amounts  of  clay.  They  were  allowed  to  harden 
in  water  for  a  week,  and  were  then  exposed  on  the  roof  of  the  office 
building  for  two  and  one-half  years,  when  they  were  broken.  All  of 
the  briquettes  appeared  to  be  in  perfectly  good  condition,  with  sharp, 
hard  edges.  Their  average  tensile  strengths  in  pounds  per  square 
inch  are  shown  in  the  following  table  :  — 

Table  No.  19. 

Portland  Cement  1 ;  Sand  2 402 

Clay  0.5 262 

"  "  "  "1.0 256 

"  "  "  "1.5 182 

"  "  "  "2.0 178 

The  mortars  with  clay  show  a  very  fair  degree  of  strength,  and 
the  tests  confirm  the  belief  that  the  presence  of  clay  works  little,  if 
any,  harm.  Tests  of  mortars  made  with  lime  and  clay  also  gave 
favorable  results.  Such  mortars  would  stand  up  in  water.  The  sub- 
ject is  worthy  of  further  investigation. 

Experiment  No.  14. 

Occasionally,  for  stopping  leaks  through  joints  in  the  sewers,  it 
was  found  convenient  to  use  cement  mixed  with  melted  tallow.  The 
tallow  congealed  at  once  and  held  the  water  while  the  joint  was  being- 
calked.  Briquettes  made  of  melted  tallow  mixed  with  Portland 
cement  and  sand,  equal  parts,  acquired  in  1  week,  a  tensile 
strength  of  about  40  pounds  to  the  inch.  After  a  month,  six  months, 
and  a  year,  they  were  little,  if  any,  stronger.  It  was  thought  that 
possibly  the  ammonia  in  the  sewage  might  gradually  saponify  and  dis- 
solve out  the  grease,  leaving  the  mortar  to  harden  by  itself.  Bri- 
quettes of  cement  and  tallow  were  kept  in  water,  to  which  a  little 
ammonia  was  added  from  time  to  time.  After  a  year  or  two  the  bri- 
quettes had  swelled  to  about  double  their  former  size,  but  the  cement 
had  acquired  no  strength. 

Experiment  No.  15. 

Having  occasion  to  build  with  concrete  a  large  monolithic  structure, 
in  which  a  flat  wall  would  be  subjected  to  transverse  stress,  it  was 
considered  necessary  to  make  experiments,  to  find  the  comparative 


136 


MAIN    DRAINAGE    WORKS. 


resistance  to  such  stress  of  concrete  made  with  different  cements 
and  with  different  proportions  of  sand  and  stone. 

The  cements  used  in  the  tests  were  an  English  Portland  and  a 
Rosendale,  both  good  of  their  respective  kinds.  Medium  coarse  pit 
sand  was  used,  and  screened  pebbles  about  an  inch  or  less  in  diameter. 
The  beams  were  ten  inches  square  and  six  feet  or  less  long.  They  were 
made  in  plank  moulds  resting  on  the  bottom  of  a  gravel-pit  about  four 
feet  deep.  After  the  concrete  had  hardened  sufficiently,  the  moulds 
were  removed,  and  the  undisturbed  beams  buried  in  the  pit  and  left 
for  six  months  exposed  to  the  weather.  They  were  then  dug  out,  and 
broken  with  the  results  given  in  the  table.  The  total  breaking  loads 
are  given,  including  one-half  of  the  weights  of  the  beams,  which  aver- 
aged about  150  pounds  per  cubic  foot.  The  constant,  c,  is  obtained  for 
the  formula :  — 

f     w  z=z  centre  breaking  load  in  pounds. 

1       d  zzz  depth  of  beam  in  inches. 
X   c,  in  which      -{        6  rr:  breadth  of  beam  in  inches. 

\        I  -^zi  distance  between  supports  in  feet. 

[^       cz=.  a,  constant. 


cV  X   I 
I 


Since  c  has  an  average  value,  and  there  were  gene^-ally  more  beams 
of  one  length  than  the  other,  the  value  of  c  as  given  does  not  exactly 
correspond  with  either  load  in  the  table. 


Table   No.  20. 


Proportion  of  Materials. 

Average  Centre  Breaking 
Weight  in  Pounds. 

Average 
Modulus  of 
Rupture  in 
Pounds. 

Average 
Value  of  c 
in  Pounds. 

Cement. 

Sand. 

Stone. 

Dist.  between 

Suijports, 

2'  4^". 

Dist.  between 

Supports, 
5'. 

Rosendale,  1     . 

"           1     . 
Portland,  1  .     . 

"        1  .     . 

"        1  .     . 

2 
3 
3 
4 
6 

5 
7 
7 
9 
11 

1,782 

Beams  broke 

3,926 

3,648 

2,822 

690 

in  handling. 

1,995 

1,190 

67 

176 
146 
112 

3.7 

9.8 
8.1 
6.2 

The  table  shows  that  concrete  has  a  rather  low  modulus,  especially 
when  made  of  Rosendale  cement.  When  transverse  stress  is  to  be 
opposed  it  is  very  important  to  give  ample  time  for  the  concrete  to 
harden. 


Plate   XXXI. 


4i-        4         3t         5         2i-         2  li  0 

PAHTS  or  SAND  TO  ONE  PAHT  OF  CEMENT. 


APPENDIX    A.  137 

EXPERISIENT    No.    16. 

Many  of  the  main  drainage  sewers  were  either  built  or  lined  with 
concrete,  which  was  always  smoothly  plastered  with  a  coat  of  mortar. 
It  was  important  that  this  surface  coat  should  he  especially  adapted  to 
resist  abrasion.  This  experiment  was  made  to  ascertain  the  best 
mixture  for  the  purpose.  Different  mortars  were  formed  into  blocks 
1-1  inches  square,  and,  after  hardening  under  water  for  8  months, 
were  ground  down  upon  a  grindstone.  The  blocks  were  pressed  upon 
the  stone  with  a  fixed  pressure  of  about  20  pounds.  A  counter  was 
attached  to  the  machine,  and  the  number  of  revolutions  required  to 
grind  off  0.1  inch  of  each  block  was  noted.  The  cements  used  in  the 
test  blocks  were  a  rather  coarse  English  Portland  and  a  fair  Rosendale. 

The  curves  (Plate  XXXI.)  show  the  results  obtained.  In  making 
these  curves  the  resistance  to  abrasion  opposed  by  the  Portland  cement 
mortar  in  the  proportion  of  one  part  cement  and  two  parts  sand  is 
assumed  to  be  100,  and  the  resistance  of  other  mortars  is  compared 
with  it.  The  effect  of  the  grinding  upon  the  test  blocks  is  noted  on 
the  curves,  and  explains  the  somewhat  striking  results. 

It  appears  that  cements  oppose  the  greatest  resistance  to  abrasion 
when  combined  with  the  largest  amount  of  sand  which  they  can  just 
bind  so  firmly  that  it  will  grind  off  and  not  be  pulled  out.  A  little 
less  or  a  little  more  of  sand  may  greatly  lessen  the  resistance.  For 
any  given  cement  the  proper  amount  of  sand  would,  probably,  have 
to  be  ascertained  by  experiment. 

Experiment  No.  17. 

It  is  a  prevalent  belief  among  masons  that  cement,  even  when  it 
contains  no  free  lime,  and  does  not  check,  expands  considerably  after 
setting.  It  is  stated  that  brick  fronts  laid  with  cement  mortar  (espe- 
ciall}^  of  Portland  cement)  have  been  known  to  bulge,  and  even  rise, 
owing  to  expansion  in  the  mortar.  Experiments  were  made  to  ascer- 
tain what  truth  there  was  in  this  belief.  Several  dozens  of  glass  lamp- 
chimneys  were  filled  with  mortars  made  of  various  brands  of  American 
and  Portland  cements,  both  neat  and  with  different  admixtures  of 
sand.  The  chimneys  were  immersed  in  water,  and,  without  exception, 
began  to  crack  within  three  days.  New  cracks  appeared  during  the 
following  ten  days,  after  which  time  hardly  a  square  inch  of  glass 
remained  which  did  not  show  signs  of  fracture.  This  showed  that 
the  cement  certainty  expanded,  though  very  slowly,  and  that  the  ex- 
pansion continued  for  about  two  weeks.     None  of  the  cracks  opened 


138  MAIN   DRAINAGE    WORKS. 

appreciably,  however,  so  that  the  amount  of  expansion,  which  was 
evidently  slight,  could  not  thus  be  even  approximately  determined. 

A  number  of  10-inch  cubes  were  then  made  of  similar  mortars,  with 
small  copper  tacks  inserted  io  the  centres  of  all  the  sides.  Some  of 
these  cubes  were  kept  in  the  air,  and  others  immersed  in  water,  and 
the  sizes  of  all  of  them  were  measured  frequently  by  callipers  during 
six  months.  The  increase  in  size' did  not  in  any  case  exceed  .01  inch, 
and  may  have  been  less.  This  indicated  that,  while  cement  mortars 
do  expand,  the  increase  in  bulk  in  any  dimension  does  not  exceed  .001 
part  of  that  elimension,  and  is  too  slight  to  be  of  consequence.  In 
the  case  of  the  walls  before  referred  to,  supposing  them  to  have  been 
80  feet  high,  with  five  ^-inch  joints  to  each  foot,  the  total  height  of 
mortar  would  have  been  100  inches,  and  the  extreme  expansion  of  the 
whole  could  only  have  been  .1  inch.  It  is  probable  that  the  appar- 
ent rise  was  merely  a  difference  in  elevation  caused  by  settlements  of 
partition  or  side  walls  laid  with  weaker  and  compressible  mortar. 

Experiment  No.  18. 

It  having  been  reported  that  cement  mortars  in  contact  with  wood 
had  sometimes  been  found  to  be  disintegrated,  as  if  they  might  have 
been  affected  by  the  wood  acids,  this  experiment  was  made  to  see  if 
any  such  effect  could  be  detected.  About  a  dozen  boxes  were  made, 
each  formed  of  five  different  kinds  of  wood,  viz.,  oak,  hard-pine,  white- 
pine,  spruce,  and  ash.  The  boxes  were  filled  with  different  cement 
mortars,  and  were  some  of  them  submerged  in  fresh  and  others  in  salt 
water.  Briquettes  were  also  made  of  cements  mixed  with  different 
kinds  of  sawdust.  At  the  end  of  a  year  no  effect  upon  the  cements 
could  anywhere  be  detected. 

Experiment  No.  19. 

Engineers  are  accustomed  to  insist  on  cement  mortars  being  used 
before  they  have  begun  to  set,  and  on  their  being  undisturbed  after 
that  process  has  begun.  With  cements  that  set  quickly  workmen  are 
tempted  to  retemper  tlie  mortar  after  it  has  begun  to  stiffen.  Some 
experiments  were  made  on  mortars  which  were  undisturbed  after 
first  setting,  and  others  which  were  retempered  from  time  to  time. 
Unfortunately  all  of  the  conditions  of  these  tests  were  not  accurately 
recorded,  and  the  results  are  not  considered  trustworthy.  The  follow- 
ing series  of  tests,  which  represents  an  extreme  case  not  met  with  in 
actual  practice,  may  be  of  interest. 


APPENDIX   A. 


139 


A  mortar  made  of  one  part  of  Portland  cement  and  two  parts  of 
sand  was  allowed  to  harden  for  a  week.  It  was  then  pulverized,  re- 
tempered,  and  made  into  briquettes.  These  subsequently  acquired  the 
following  tensile  strength  in  pounds  per  square  inch  :  — 

1  week .  7 

1  month 13 

6  months 49 

2  years 93 

Under  the  circumstances  it  is  somewhat  surprising  that  the  mortar 
developed  as  much  strength  as  it  did.  Good  tests  to  elucidate  this 
subject  are  much  needed. 

Experiment  No.  20. 

A  brand  of  "  Selenitic"  cement  was  offered  for  use  on  the  work,  and 
was  said  to  possess  great  merits.  It  was  made  by  treating  an  ordi- 
nary American  cement  by  a  patented  process.  It  was  tested  by  com- 
paring it  with  an  untreated  sample  of  the  same  cement  of  which  it  was 
made.     The  following  are  the  results  of  the  tests  :  — 

Table  No.  2. 


Mixture. 

Kind  of 
Cement. 

1  Day. 

1  Week. 

1  Month. 

6  Months. 

1  Tear. 

Neat .     . 
Cement . 

Untreated 
Selenitic 

124 
149 

185 
168 

140 
171 

164 

282 

186 
273 

Cement,  1 
Sand,  1.5 

Untreated 
Selenitic 

121 
120 

176 

158 

296 
276 

316 
356 

Cement,  1 
Sand,  2  . 

Untreated 
Selenitic 

92 
103 

154 
133 

259 
226 

805 
276 

Cement,  1 
Sand,  4  . 

Untreated 
Selenitic 

88 
49 

87 
97 

158 
167 

168 
164 

The  breakings  are  somewhat  irregular,  but  seem  to  show  that  this 
cement  was  made  somewhat  stronger  by  the  selenitic  process  of 
treatment  when  tested  neat,  but  was  little,  if  at  all,  improved  for  use 
as  a  mortar  ;  not  enough,  certainly,  to  compensate  for  the  higher  cost. 


APPENDIX  B. 


LIST    OF   OFFICERS     CONNECTED   WITH    BOSTON 
MAIN  DRAINAGE   WORKS, 


Commission   of   1875. 

E.    S.    CHESBROUGH,   C.E. 
MOSES   LANE,   C.E. 
C.   F.    FOLSOM,   M.D. 

Engineers. 

City  Engineers. 

Joseph  P.  Davis 1876-1880. 

Henry  M.  Wightman 1880-1885. 

Principal  Assistants  to  City  Engineer. 

Henry   M.  Wightbian 1876-1880. 

Alphonse   Fteley ^ 1880-1884. 

Principal  Assistant  in  Charge  of  Main  Drainage   WorTcs. 

Eliot   C.  Clarke 1876-1885. 

Assistant  Engineers. 

William  Jackson 1876-1885. 

Frederic   P.  Stearns 1880-1885. 

Clemens  Herschel 1878-1880. 

George    S.  Rice 1877-1880. 

George   H.  Crafts 1877-1881. 

Seth  Perkins 1877-1885. 

Charles   S.  Gowen 1880-1881. 

E.  R.  Howe 1877-1880. 

F.  A.  May 1876-1880. 

F.  W.  Ring 1876-1877. 

K.    Tappan 1876-1877. 


APPENDIX    B. 


141 


Principal    Superintendents   of  Construction. 
Sewer    Construction. 
H.  A.  Carson. 

Pumping- Static  n . 
S.  H.  Tarbell. 


Joint   Special   Committee   on   Improved   Sewerage. 
1876. 


Aldermen. 

Alvah   a.  Burrage,  Chairman. 
Solomon   B,  Stebbins. 
Thomas  J.  Whidden. 


1877. 


Aldermen. 

Choate   Burnham,  Chairman. 
Charles   W.  Wilder. 
Lucius   Slade. 


1878. 

Aldermen. 

Thomas  J.  Whidden,  Chairman. 
Solomon   B.  Stebbins. 
Lucius   Slade. 


Councilmen. 

Eugene   H.  Sampson. 
J.  Homer   Pierce. 
Warren   K.  Blodgett. 
Marcellus   Day. 
Albert   H.  Taylor. 

Councilmen. 

Eugene  H.  Sampson. 
J.  Homer  Pierce. 
Warren   K.  Blodgett. 
Martin   L.  Ham. 
George  L.  Thorndike. 

Councilmen. 

Eugene   H.  Sampson. 
George  L.  Thorndike. 
J.  Homer   Pierce. 
Frederick   B.  Day. 
James  B.  Richardson. 


1879. 


Aldermen.  * 

Lucius   Slade,  Chairman. 
Solomon  B.  Stebbins. 
Daniel   D.  Kelly. 


Councilmen. 

Isaac  Rosnosky. 
Thomas   J.  Denney. 
John   P.  Brawley. 
Daniel    J.  Sweeney. 
Oscar  B.  Mowry. 


142 


MAIN   DEAINAGE   WORKS. 


1880. 


Aldermen. 

Lucius   Slade,  Chairman. 
Asa    H.  Caton. 
Geobge  L.  Thorndike. 


Councilmen. 

Daniel   J.  Sweeney. 
Chaeles   H.  Plimpton. 
Howard    Clapp. 
Malcolm   S.  Geeenough. 
Benjamin  Brintnall. 


1881. 


Aldermen. 

Lucius    Slade,  Chairman. 
William   Woolley. 
Charles  H.   Hersey. 


Councilmen. 
Howard   Clapp. 
Thomas   J.  Denney. 
Malcolm   S.  Greenough. 
Frank  E.  Farwell. 
John   E.  Bowker. 


1882. 


Aldermen. 

Lucius   Slade,  Chairman. 
William   Woolley. 
Charles  H.  Hersey. 


Councilmen. 

Malcolm  S.  Greenough. 
Thomas   J.  Denney. 
Frank   E.  Farwell. 
Prentiss   Cummings. 
Nathan   G.  Smith. 


1883. 


Aldermen. 

Lucius   Slade,  Chairman. 
William  Woolley. 
Thomas  H.  Devlin. 


Councilmen. 

Malcolm   S.  Greenough. 
Thomas  J.  Denney. 
Frank   E.  Farwell. 
John   B.  Fitzpatrick. 
Patrick  J.  Donovan. 


1884. 


Aldermen. 

Lucius   Slade,  Chairman. 
Charles   H.  Hersey. 
Malcolm  S.  Greenough. 


*  Councilmen. 

Thomas   J.  Denney. 
Patrick  J.  Donovan. 
Isaac  Rosnosky. 
J.  Edward   Lappen. 
James  B.  Graham. 


APPENDIX   B. 


143 


1885. 
Aldermen. 

Patrick  J.  Dokovan,  Chairman. 
George'  Curtis. 
William  J.  Welch. 


Councilmen. 

Edward   P.  Fisk. 
J.  Edward   Lappen. 
John   Gallagher. 
William   H.  Murphy. 
Benjamin   B.  Jenks. 


ii 


3  Jiipi 


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